, 


UNIVERSITY  OF  CALIFORNIA 

ANDREW 

SMITH 

HALLIDIE.: 


186831^1901 


m 


THE 


SLIDE-VALVE  AND  ITS 
FUNCTIONS 


WITH 


SPECIAL  REFERENCE  TO  MODERN  PRACTICE 


IN    THE 


UNITED  STATES 


WITH    90    DIAGRAMS    AND    ILLUSTRATIONS 


BY 

JULIUS   BEGTRUP,  M.  E 


NEW  YORK 
D.    VAN     NOSTRAND     COMPANY 

LONDON 

E.    &     F.     N.   SPON,    LIMITED.,     125    STRAND 
1902 


HALLIDIE 


CoPYRIGHTr 
BY 

D.  VAN  NOSTRAND  COMPANY. 


TYPOGRAPHY  BY  C.  J.  PETERS  &  SON, 
BOSTON,  MASS.,   U.  S.  A. 


PREFACE. 


,,  THE  Slide- Valve  has  been  called  the  heart  of  the  steam  en- 
gine, and  the  simile  is  not  badly  chosen  ;  for  the  valve  is  a  dis- 
tinct and  vital  part  of  the  engine,  controlling  and  regulating  the 
circulation  of  its  life-fluid  in  a  manner  not  entirely  unlike  that 
of  a  living  heart.  It  is  the  office  of  the  slide-valve  to  direct  the 
motion  and  action  of  this  subtile  and  expensive  fluid  to  best  ad- 
vantage and  without  waste,  so  as  to  make  the  engine  an  effective 
and  economical  motor. 

As  the  valve  must  be  designed  so  as  to  effect  an  economical 
steam  distribution  in  the  cylinder,  it  has  attained  a  peculiar  sig- 
nificance in  scientific  steam  engine  construction;  but  durability 
and  permanency  of  form  are  requirements  not  less  imperative, 
and  they  involve  constructive  problems  of  a  different  order.  In 
recognition  of  this  fact  an  attempt  has  been  made  in  this  work 
to  treat  the  subject  with  due  regard  to  the  various  requirements 
of  modern  practice.  The  fundamental  principles  are  fully  ex- 
plained, and  are  illustrated  by  new  graphical  methods,  and  a 
number  of  special  valve  constructions  are  described  and  analyzed, 
in  order  to  exhibit  in  a  comprehensive  manner  how  the  exacting 
conditions  of  higher  steam  pressure  and  higher  speed  have  been 
met  by  modern  engine-builders. 

An  endeavor  has  been  made  to  present  the  subject-matter 
of  this  book  in  a  condensed  form,  as  being  best  adapted  to  the 
requirements  of  practical  men,  and  the  author  has  in  this  re- 
spect followed  the  suggestions  of  an  extensive  personal  experi- 
ence. 


f\  C\   s~i   n  ^ 


IV  PREFACE. 

The  information  is  presented  in  more  or  less  explanatory 
form,  which  is  necessary  in  order  to  preserve  its  scope  and  gen- 
eral character  by  the  absence  of  a  multiplicity  of  details  ;  but 
lengthy  explanations  are  studiously  avoided,  for  it  is  the  author's 
opinion  that  practical  knowledge  —  which  is  the  more  complete 
knowledge  —  cannot  be  imparted  by  the  use  of  many  words. 
Nothing  is  fully  comprehended  before  the  learner  can  follow  the 
thoughts  of  the  teacher,  but  he  must  be  allowed  to  learn  this 
in  his  own  way,  or  by  his  own  efforts,  if  the  acquired  knowledge 
is  to  be  of  any  actual  use.  All  the  book  really  can  accomplish 
is  to  start  the  reader  thinking  in  the  right  direction,  which  often 
may  be  done  by  a  few  carefully  selected  words. 

Both  verbal  and  graphical  demonstrations  are  used,  that  one 
form  may  supplement  the  other.  The  verbal  treatment  is  the 
broader,  but  the  graphical  representation  is  indispensable  as  an 
illustrative  and  explanatory  supplement,  and  as  far  as  the  valve 
motion  is  concerned,  it  is  the  only  method  practiced  by  those 
who  build  engines,  or  make  the  drawings  from  which .  they  are 
built.  Further,  the  graphical  representation  has  the  advantage 
that  it  presents  a  number  of  associated  facts  in  one  frame,  as  it 
were  ;  and  it  may,  therefore,  eventually  lead  to  those  broad  con- 
ceptions which  are  of  so  great  practical  utility,  and  which  the 
best  verbal  exposition  sometimes  may  fail  to  disclose. 

The  valve-diagrams  presented  in  this  book  have  been  used 
for  the  last  ten  years,  on  many  different  occasions,  and  they 
have  given  more  general  satisfaction  than  others  which  are 
better  known ;  and  the  reader  will  doubtless  share  this  opinion, 
if  the  methods  here  used  are  accorded  a  fair  trial. 

Comparatively  few  letters  of  reference  are  used  in  the  text, 
and  it  is  believed  that  this  will  make  it  easier  to  follow  the  dem- 
onstrations. 

J.   BEGTRUP. 
JERSEY  CITY,  N.  J.,  January,  1902. 


TABLE   OF   CONTENTS. 


CHAPTER   I. 

THE    COMMON    SLIDE-VALVE. 

PACK 

INTRODUCTORY  REMARKS       .     .     .-.•..•.•.•.  .........  r 

THE  COMMON  D-VALVE       i  •,.    r   .....  2 

SIMPLEST  FORM  OF  SLIDE-VALVE     .     .     .     .'.'.     .     .     .T'  ...     ...  4 

THE  VALVE-MOTION   IN  RELATION  TO  THE  PISTON-MOTION      ....  9 

VALVES  WITHOUT  LAP        .     .     . fc    .    .     .     .     .  n 

THE  PRIMITIVE   VALVE-DIAGRAM .,.,.....  12 

SWEET'S  VALVE-DIAGRAM 14 

VARIABLE  VALVE  TRAVEL        .     .     ,     .     . 15 

LIMITATIONS  OF  THE  COMBINATION  VALVE 16 

STEAM-PORTS     *.   -.   •.  '.  •.  -^  -„  '...'.     .  '.     .  ;.     .     .     .    *     .    .-'.  18 

PORT-OPENING *.  •. 19 

VALVE  DIMENSIONS 20 

VALVE  DIAGRAM  FOR  SHIFTING-ECCENTRIC  ENGINES 21 

VARIATION  IN    PORT-OPENING 24 

NOTES  ABOUT  LEAD 25 

COMPRESSION       / 27 

THE  MOTION  OF  LOCOMOTIVE  VALVES      .......,'....  28 

MULTIPORTING        .       .       .       .... 31 

SETTING  THE  ENGINE  ON  DEAD  CENTERS     . 32 

CHAPTER    II. 
IMPROVED  SLIDE-VALVES. 

THE  DOUBLE-PORTED  MARINE  SLIDE-VALVE 34 

THE  ALLEN   LOCOMOTIVE  VALVE 35 

THE  STRAIGHT-LINE   BALANCED  VALVE 36 

VARIATIONS  OF  THE    STRAIGHT-LINE  VALVE 38 

THE  McEwEN   VALVE 39 

THE  BALL  TELESCOPIC  VALVE 41 

BALANCING  A  COMMON  D-VALVE 42 

THE  RICHARDSON   BALANCED  VALVE 44 

v 


vi  TABLE    OF  CONTENTS. 

PAGE 

THE  THOMAS  BALANCE 44 

PISTON-VALVES 46 

VALVES  OF  THE  "IDEAL  ENGINE" 47 

THE  WESTINGHOUSE  STANDARD  VALVE 49 

VALVES  ON  COMPOUND  ENGINES 50 

THE  WESTINGHOUSE  COMPOUND  VALVE 53 

THE  VAUCLAIN  VALVE 54 

THE  ALLFREE  VALVE-GEAR 57 

CHAPTER    III. 
FOUR-VALVE  SYSTEMS. 

INTRODUCTORY  REMARKS 61 

CORLISS  VALVES 62 

LIMITATIONS  OF  THE  CORLISS  GEAR 65 

THE  SINGLE-ECCENTRIC  VALVE  DIAGRAM 67 

Two  ECCENTRICS 69 

CORLISS  VALVE  DIMENSIONS 71 

DIRECTIONS  FOR  SETTING  THE  VALVE-GEAR 72 

VALVES  OF  THE  PORTER-ALLEN  ENGINE 72 

GRIDIRON  VALVES 75 

THE  HILL  VALVES - 76 

THE  WHEELOCK  VALVES 78 


CHAPTER   IV. 
INDEPENDENT  CUT-OFF. 

INTRODUCTORY  REMARKS 80 

THE  CUT-OFF  VALVE  ON  A  STATIONARY  VALVE-SEAT 81 

THE  CUT-OFF  VALVE  ON  THE  BACK  OF  THE  MAIN  VALVE      ....  83 

FUNDAMENTAL  PRINCIPLES       83 

^THE  MEYER  CUT-OFF 85 

THE  MEYER  CUT-OFF  DIAGRAM »  86 

LIMITATIONS  OF  THE  MEYER  CUT-OFF 89 

THE  RIDER  CUT-OFF  VALVE 89 

CUT-OFF  VARIED  BY  ROTATING  ECCENTRIC  ON  SHAFT 90 

GRIDIRON  VALVES  WITH  INDEPENDENT  CUT-OFF 96 

BEGTRUP'S  ECCENTRIC 97 

CUT-OFF  VALVE  WITH  CONSTANT  TRAVEL  ON  MAIN  VALVE  ....  99 

THE  BUCKEYE  VALVE-GEAR I02 

PISTON-VALVES  WITH  INDEPENDENT  CUT-OFF 105 

CUT-OFF  VALVE  WORKED  BY  MEANS  OF  A  LINK 106 

INDEPENDENT  CUT-OFF  ON  FOUR- VALVE  ENGINES 108 


TABLE    OF  CONTENTS.  vii 

PAGE 

THE  MclNTOsH  &  SEYMOUR  VALVES 108 

VALVES  OF  THE  RUSSELL  ENGINES       no 

THE  BUCKEYE  VIBRATING  CUT-OFF in 

CHAPTER   V. 
THE  SLIDE-VALVE  ON  PUMPS. 

BLAKE 117 

DEAN  BROTHERS 119 

KNOWLES 121 

DAVIDSON 121 

CAMERON 123 

WORTHINGTON 124 

CHAPTER   VI. 
ANGULARITY  OF  CONNECTING-ROD  AND  ECCENTRIC-ROD. 

THE  ANGULAR  MOTION  OF  THE  CONNECTING— ROD 128 

THE  ANGULAR  MOTION  OF  THE  ECCENTRIC-ROD 132 

STEAM-  AND  EXHAUST-LAPS 134 

EQUALIZING  BOTH  LEAD  AND  CUT-OFF 134 

THE  INCLINED  ROCKER  FOR  SHIFTING—ECCENTRIC  ENGINES      ....  136 

EQUALIZING  THE  LEAD  ON  SHIFTING-ECCENTRIC  EVGINES       ....  137 

UNEQUAL  LAPS  ON  VARIABLE  CUT-OFF  ENGINES    .    , 139 


THE  SLIDE-VALVE  AND   ITS   FUNCTIONS, 


CHAPTER    I. 

THE   COMMON    SLIDE-VALVE. 
INTRODUCTORY    REMARKS. 

THE  term  "  slide-valve  "  is  applied  to  flat-faced  valves  having 
a  continuous  reciprocating  sliding  motion,  whereby  steam  is 
alternately  admitted  to  and  exhausted  from  a  cylinder ;  and  this 
term  will  also  apply  to  similar  parts  of  gas,  air,  and  water 
engines  and  pumps.  The  steam  engine  slide-valve  and  some 
typical  pump  valves  will  be  considered  here. 

The  sliding  surfaces  may  be  cylindrical,  and  this  does  not 
affect  the  principles  of  the  valve  motion ;  but  in  such  case  dif- 
ferent names  are  used,  as  piston-valve,  Corliss-valve,  semi-rotary 
or  oscillating  valve,  etc.  These  valves  are  only  modifications 
of  the  original  slide-valve,  and  they  will  be  included  as  such  here.  //  i~ 

Slide- valves,  of  whatever  design,  can  easily  be  referred  to 
and  compared  with  the  common  D-valve,  their  functional  prop- 
erties, in  all  cases,  being  closely  related.  But  the  D-valve  — 
so  called  because  in  section  slightly  similar  to  the  letter  D  —  is 
not  the  simplest  slide-valve,  per  sc  ;  and  in  order  to  fully  under- 
stand the  principles  and  master  the  analysis  of  the  subject,  it 
is  advisable  to  commence  with  a  careful  study  of  the  simplest 
elementary  form. 

By  thus  taking  up  the  elements  of  the  subject,  or  going  to 
the  bottom  of  it,  as  it  were,  the  consequent  study  of  more  or 

1 


2  THE  SLIDE-VALVE  AND   ITS  FUNCTIONS. 

less  elaborate  forms  and  combinations  will  be  greatly  facilitated  ; 
and  such  a  course  may  lead  to  broad  and  independent  views,  so 
essential  to  successful  and  progressive  engineering. 

The  diagrams  presented  in  this  chapter  are  not  supposed  to 
represent  actual  practice.  They  are  only  here  to  illustrate  and 
explain  the  text,  and  to  give  graphical  directions  for  laying  out 
the  essential  parts  of  valve  and  gear,  and  no  attempt  is  made  to 
show  details.  Some  of  the  sketches  are  purposely  out  of  pro- 
portion, for  otherwise  almost  unlimited  space  would  be  required, 
or  else  clearness  and  distinctness  of  the  principal  parts  would  be 
sacrificed  ;  and  it  can  hardly  be  considered  a  serious  defect,  for 
some  imagination  is  a  prerequisite  in  constructive  engineering, 
for  which  there  is  no  substitute. 


THE    COMMON    D-VALVE. 

Fig.  i  shows  the  valve  in  its  central  position  and  part  of 
the   cylinder.     By    moving   the   valve    to    the   right    steam    is 

exhausted  from  the  right 
hand  side  of  the  cylinder 
and  admitted  to  the  left 
hand  side ;  and  by  moving 
it  to  the  left  steam  is  ex- 
hausted from  the  left  hand 
side,  and  admitted  to  the 
right  hand  side.  Steam  is 
admitted  past  the  outer  edges 


of  the  valve,  and  the  exhaust 


Fig.  i. 

escapes  past  the  inner  edges  into  the  exhaust-cavity,  and  from 
thence  to  the  exhaust -pipe  (not  shown). 

The  flat  surface  on  which  the  valve  slides  is  called  the  valve 
face  of  the  cylinder  or  the  valve-seat,  and  the  corresponding 
surface  of  the  valve  is  the  face  of  the  valve.  The  orifices  of 
steam -passages,  covered  by  the  face  of  the  valve,  are  the  steam- 


THE    COMMON  SLIDE-VALVE.  3 

ports,  and  the  central  opening  in  the  cylinder  casting  is  called 
the  exhaust-port. 

The  conventional  use  of  this  term  is  somewhat  unfortunate, 
for,  as  the  exhaust  from  the  cylinder  passes  out  through  the 
same  ports  through  which  steam  is  admitted,  these  ports  are 
also  entitled  to  be  named  exhaust-ports.  True,  the  terms  steam 
and  exhaust  signify  here  only  different  conditions  of  the  steam, 
but  the  name  "  exhaust-port  "  for  the  middle  opening  conveys 
unconsciously  the  impression  that  the  two  exterior  ports  are  for 
steam  only,  and  the  central  port  is  for  the  exhaust.  Besides, 
the  name  port  is  too  dignified  in  this  connection,  where  it  only 
means  a  hole  or  opening  through  which  the  exhaust  escapes 
after  it  has  left  the  steam-port,  and  no  particular  importance 
attaches  to  this  hole  ;  it  can  be  of  any  shape  and  size,  provided 
it  is  big  enough  ;  in  fact,  it  hardly  needs  a  special  name. 

The  steam-ports,  on  the  other  hand,  are  essential  and  char- 
acteristic components  of  the  valve-face,  for  in  conjunction  with 
the  valve,  they  regulate  the  steam  distribution  in  the  cylinder, 
and  their  location  and  dimensions  require  careful  consideration. 
Engines  having  separate  exhaust-valves  have  also  separate 
exhaust-ports,  but  these  bear  no  relation  to  the  "exhaust -port," 
so  called,  of  the  common  D-valve.  The  force  of  this  argument 
will  become  apparent  later  on. 

That  part  of  the  face  of  the  valve  which  overlaps  the  out- 
side edge  of  the  steam-port,  when  the  valve,  Fig.  i,  is  in  its 
central  position,  is  called  steam-lap,  and  the  over-lapping  of  the 
inside  edges  is  called  exhaust-lap.  The  terms  "inside"  and 
"  outside  "  lap  are  often  used,  but  are  not  to  be  recommended, 
for  many  valves  have  steam-lap  on  the  inside  and  exhaust-lap  on 
the  outside.  Valves  are  often  constructed  without  exhaust-lap, 
and  occasionally  the  exhaust-edge  of  the  valve  does  not  reach 
to  the  port-edge,  in  which  case  the  face  of  the  valve  does  not 
entirely  cover  the  ports  in  its  central  position,  and  the  un- 
covered part  is  then  referred  to  as  negative  exhaust-lap  or 


4  THE   SLIDE-VALVE   AND   ITS  FUNCTION'S. 

exhaust  clearance.  If  not  otherwise  specified,  lap  means  steam- 
lap.  The  two  partitions  which  separate  the  steam-ports  from 
the  exhaust -opening  are  named  bridges. 

It  is  proper  to  study  the  slide-valve  as  it  relates  to  the 
action  of  steam  on  one  side  of  the  piston  only  ;  for  in  a  double- 
acting  cylinder,  being,  as  it  were,  a  combination  of  two  single- 
acting  cylinders,  the  action  on  one  side  of  the  piston  is 
practically  an  exact  repetition  of  that  on  the  other  side ;  and 
the  D-valve  can  be  divided  into  two  equal  halves,  each  of  which 
will  take  care  of  the  steam  on  one  side  of  the  piston ;  and  in 
order  to  place  the  back  pressure  in  its  proper  relation  to  the 
forward  stroke,  -it  is  only  necessary  to  consider  the  exhaust- 
action  in  reversed  order. 

The  duty  of  the  slide-valve,  broadly  speaking,  is  to  admit 
steam  during  the  forward  stroke  and  exhaust  it  during  the 
return  stroke,  and  which  includes  expansion  and  compression. 

The  majority  of  engines  are  double-acting  ;  that  is,  steam  is 
admitted  alternately  on  both  sides  of  the  piston,  and  the  com- 
mon slide-valve  is  charged  with  the  fourfold  duty  of  admitting 
and  releasing  steam  at  both  ends  of  the  cylinder ;  and  we  may 
conceive  this  being  attained  by  a  unification  of  four  valves  in 
one  body.  The  regularly  alternating  periods  of  admission  and 
exhaust,  and  the  symmetrical  arrangement  of  steam-ports  admit 
of  a  single  valve  being  used. 

SIMPLEST    FORM    OF    SLIDE-VALVE. 

Fig.  2  represents  a  slide-valve,  whose  only  duty  is  to  open  and 
close  for  admission  of  steam  to  one  side  of  the  piston.  When  it 
is  moved  to  the  right,  a  sufficient  distance,  it  uncovers  part  of 
the  port  and  admits  steam  to  the  cylinder,  and  by  its  retrograde 
motion  the  port  is  closed  again.  It  controls  the  admission  of 
steam  only,  and  there  will  have  to  be  another  valve  to  open  and 
close  for  the  exhaust ;  and  in  case  of  a  double-acting  engine  two 
such  pairs,  or  four  valves  in  all,  would  be  needed. 


THE    COMMON  SLIDE-VALVE. 


The  reciprocating  motion  of  slide-valves  is  generally  pro- 
duced by  eccentrics  attached  to  the  crank  shaft  of  the  engine, 
and  an  eccentric  —  being  nothing  but  an  enlarged  crank-pin  — 


Fig.  2. 


Fig.  3. 


Fig.  4- 


Fig.  5- 


is  in  the  annexed  diagrams '  represented  by  a  small  crank,  or 
arm,  E,  and  which  communicates  motion  to  the  valve  through 
a  rod,  as  indicated.  The  diameter  of  the  circle  described  by 


6  THE   SLIDE-VALVE   AND   ITS  FUNCTIONS. 

the  center  of  the  eccentric  is  called  the  throw  of  the  eccen- 
tric, and  it  represents  here  the  full  stroke  or  travel  of  the 
valve. 

According  to  this  definition  the  throw  of  an  eccentric  is 
twice  its  eccentricity  or  radius  ;  but,  as  the  throw  of  a  crank 
means  the  distance  from  center  of  shaft  to  center  of  crank-pin, 
it  ought  to  mean  the  same  when  speaking  of  an  eccentric. 
However,  rhetoric  is  not  cultivated  in  the  shop  or  engine  room, 
and  when  they  talk  about  the  throw  of  an  eccentric  it  is  well 
understood  what  it  means. 

For  convenient  representation  in  a  limited  space,  the  dis- 
tance between  eccentric  and  valve  is  made  short  in  the  diagram, 
which  makes  the  angularity  of  the  eccentric-rod  appear  ab- 
normal. In  ordinary  stationary  engines  this  angularity  is 
always  very  slight,  and  its  effect  on  the  valve  motion  may  be 
ignored ;  and  for  this  reason  we  may  assume  the  eccentric-rod 
parallel  with  its  medial-line  of  action,  as  also  would  be  the  case 
if  we  assume  an  eccentric-rod  of  infinite  length.* 

Fig.  3  shows  the  valve  in  the  position  where  it  commences 
to  open  the  steam-port.  Edge  A  of  the  valve  and  edge  B  of 
the  port  are  now  "  line  and  line,"  and  by  continued  turning 
of  the  eccentric  in  the  direction  shown  by  the  arrow,  these 
edges  will  separate,  leaving  an  increasing  opening  for  the  pas- 
sage of  steam,  till  the  eccentric  has  reached  the  extreme  of  its 
throw,  when  by  further  turning  it  will  push  the  valve  back 
towards  edge  B  ;  and  when  the  eccentric  is  in  position  4,  verti- 
cally opposite  position  I,  the  port  is  closed  again. 

It  should  be  observed  that  we  are  here  only  considering 
one  edge  of  the  valve  and  one  edge  of  the  steam-port ;  other  re- 
lations of  port  and  valve  being  for  the  present  quite  immaterial. 
These  edges  come  together  twice  during  each  revolution  of  the 
eccentric,  when  it  is  at  the  vertically  opposite  points  r  and  4, 

*  The  actual  effect  produced  by  the  angular  motion  of  the  eccentric-rod  is  explained  in  the 
last  chapter  of  the  book. 


THE    COMMON  SLIDE-VALVE.  7 

and  the  valve,  therefore,  opens  and  closes  the  port  once  during 
each  revolution. 

If  arc  1-4  represents  the  period  during  which  the  port  is 
open,  arc  4-1  will  represent  the  period  during  which  it  is  closed. 
The  greatest  port  opening  is  equal  to  the  distance  G-3,  and  for 
any  position  of  the  eccentric,  the  corresponding  port  opening 
can  be  measured  horizontally  on  the  shaded  segment.  When 
the  eccentric  is  at  "  half  throw, "  at  point  10,  the  valve  is  in 
the  position  shown  in  Fig.  2,  and  the  amount  it  overreaches  the 
port  in  this  position  is  the  "  lap,"  and  which  is  equal  to  the 
distance  L.  Thus  the  length  of  the  period  during  which  steam 
is  admitted  depends  on  the  amount  of  lap,  for  the  valve  must 
move  from  its  middle  position  a  distance  equal  to  the  lap  before 
it  uncovers  the  steam-port,  and  it  is  evident,  that  the  longer  the 
period  during  which  the  port  is  closed  the  shorter  must  be  the 
period  during  which  it  is  open.  A  correct  idea  of  this  relation- 
ship can  be  had  by  an  inspection  of  the  figure,  which  clearly 
shows  how  an  increase  or  diminution  of  distance  L  affects  the 
period  of  steam  admission. 

Comparing  the  valve  here  described  with  that  shown  in  Fig, 
i  it  will  be  seen,  that  by  cutting  off  one-half  of  the  latter  and 
filling  up  the  exhaust-cavity,  we  have  a  valve  very  similar  to 
that  shown  in  Fig.  2,  and  operating  in  exactly  the  same  manner. 
It  will  also  readily  be  seen  that  a  valve  like  that  shown  in  Fig. 
2,  working  in  a  separate  chamber,  could  be  made  to  open  and 
close  an  exhaust-port  in  much  the  same  manner  as  the  steam- 
valve  controls  the  admission  of  steam  or  as  one  of  the  inner 
edges  of  the  D-valve,  Fig.  T,  controls  the  exhaust,  and  that  the 
period  of  exhaust  for  each  turn  of  the  eccentric  would  depend 
on  an  exhaust-lap  corresponding  to  the  steam-lap  in  Fig  2  or 
the  exhaust -lap  in  Fig  i. 

Fig.  5  shows  an  exhaust-valve  and  its  eccentric  at  half 
throw ;  the  main  difference  between  this  valve  and  the  steam- 
valve,  Fig.  2,  being  that  in  Fig.  5  the  valve  is  turned  end  for 


8  THE  SLIDE-VALVE  AND   ITS  FUNCTIONS. 

end  and  has  a  smaller  lap,  which  makes  the  period  of  exhaust 
longer  than  the  period  of  admission.  It  would  also  be  necessary 
to  provide  means  for  holding  this  valve  to  its  seat,  which  is  not 
shown. 

The  period  of  exhaust  is  represented  by  the  arc  of  the 
shaded  segment,  Fig.  5.  If  the  exhaust  eccentric  is  fixed  on 
the  shaft  in  the  same  position  as  the  steam  eccentric,  the 
period  of  exhaust  will,  in  a  manner,  be  diametrically  opposite 
the  period  of  admission  ;  that  is,  if  we  imagine  the  period  of 
revolution  represented  by  a  circle.  Under  such  conditions,  it  is 
evident  that  all  four  valves  for  a  double  acting  engine  might  be 
driven  by  one  eccentric ;  and  by  uniting  the  four  valves  in  one 
body,  and  by  providing  an  exhaust  cavity  to  keep  the  exhaust 
separate  from  the  live  steam,  we  arrive  at  the  construction 
shown  in  Fig.  V? 

It  should  be  noted  again,  that  here  the  exhaust  passes 
through  a  port  which  also  serves  for  admission  of  steam,  and 
that  steam  passes  over  the  outer  edge  of  this  port  on  its  way 
to  the  cylinder,  and  is  exhausted  from  the  cylinder  over  the 
opposite  edge,  and  that  the  steam-  and  exhaust-lap,  therefore, 
extend  in  opposite  directions,  as  on  the  separate  valves  Figs.  2. 
and  5.  Each  operation  of  this  valve,  therefore,  depends  on  the 
relative  position  of  two  individual  edges,  just  as  does  each 
operation  of  the  simple  valves  referred  to ;  and  thus  is  estab- 
lished the  proposition  that  such  simple  valves  are,  in  a  sense, 
integral  parts  of  the  D-valve,  or,  in  other  words,  the  D-valve  is 
equivalent  to  four  simple  valves  driven  by  one  eccentric. 

Let  the  circle  in  Fig.  6,  p.  12,  represent  the  path  of  the 
center  of  the  eccentric,  and  arcs  1-4  and  6-9  represent  steam 
and  exhaust  periods  respectively,  during  one  revolution  of  the 
eccentric,  for  the  left  half  of  the  D-valve,  and  the  left  side  of 
the  piston.  It  is  here  observable  that  the  greatest  steam  and 
exhaust  openings  occur  when  the  valve  is  at  the  two  extremes 
of  its  travel,  that  is,  at  diametrically  opposite  points  of  the 


THE    COMMON  SLIDE-VALVE.  9 

period  of  revolution;  that  any  opening  of  the  port  can  be 
measured  horizontally  on  the  segments  ;  that  if  there  be  no 
exhaust  lap,  the  exhaust  period  will  cover  one-half  revolution  ; 
and  that  lap  plus  port-opening  equals  half  travel  of  valve. 


THE    VALVE-MOTION    IN    RELATION    TO   THE    PISTON-MOTION. 

The  main  object  of  the  discussion  so  far  has  been  to  es- 
tablish a  clear  conception  of  the  simple  relationship  which 
exists  between  laps  and  periods  of  admission  and  exhaust.  The 
next  subject  for  consideration  is  the  relation  of  these  periods  to 
the  motion  of  the  piston  in  the  cylinder,  which  includes  deter- 
mination of  the  position  of  the  eccentric  relative  to  the  crank. 
It  has  been  shown  how  these  periods  may  be  lengthened  .or 
shortened  by  changing  the  laps  of  the  valve  ;  and  any  one  of 
them  can  evidently  be  made  to  coincide  with  any  period  of  the 
piston-stroke  by  fixing  the  eccentric  in  a  suitable  position  on  the 
crank-shaft. 

First  :  Where  should  the  valve  be  when  the  piston  is  at  the 
end  of  the  cylinder  and  commencing  its  forward  stroke  ?  As 
the  port  must  open  at  or  near  the  beginning  of  the  piston- 
stroke,  when  the  crank  is  on  its  first  "  dead  center, "  and  as  the 
period  of  admission  occurs  during  the  opposite  half-revolution  of 
the  eccentric,  and  must  be  considerably  less  than  one-half  period 
of  revolution,  it  follows  that  the  eccentric  must  be  past  the 
middle  of  its  throw,  or  more  than  one-quarter  of  a  revolution 
ahead  of  the  crank.  Let  C,  Fig.  3,  represent  the  crank  when 
the  valve  is  at  the  point  of  admitting  steam,  at  I,  then  consider- 
ing that  eccentric  and  crank  are  moving  together  with  the  crank 
shaft,  it  is  clear  that  when  the  crank  has  arrived  at  the  end  of 
its  return  stroke,  at  C,  Fig.  4,  the  eccentric  has  advanced  the 
same  angular  distance,  from  position  i  to  2,  and  there  will  be 
a  small  opening  between  the  valve  and  the  port-edge,  as  shown  ; 
and  during  this  short  interval  steam  enters  the  cylinder  in  ad- 


10  THE   SLIDE-VALVE  AND   ITS  FUNCTIONS. 

vance  of  the  piston.  This  initial  port  opening  is  called  lead  or 
sometimes  steam-lead,  in  contradistinction  from  exhaust-lead, 
which  means  the  opening  for  exhaust  at  commencement  of  the 
return  stroke.  Steam-lead  is  usually  supposed  beneficial,  and 
the  desirability  of  exhaust-lead  is  unquestionable.  Lead  is  in- 
creased by  turning  the  eccentric  forward  on  the  shaft,  and  is 
diminished  by  turning  it  backward. 

Sometimes,  under  certain  conditions,  the  port  opens  after 
the  forward  stroke  has  commenced,  and  in  such  case  the  ex- 
pression "  negative-lead "  may  be  used,  to  indicate  that  the 
valve  overlaps  the  steam-port  to  a  certain  extent  at  the  com- 
mencement of  the  stroke. 

Let  the  position  of  the  eccentric  at  the  beginning  of  the 
stroke  be  at  2,  Fig.  4 ;  then  period  of  admission  from  the  time 
the  piston  starts  on  its  forward  stroke  is  represented  by  arc 
2-4,  which  obviously  always  should  be  considerably  less  than 
the  period  of  one-half  revolution  in  order  to  provide  for  expan- 
sion of  the  steam.  The  angle  10-2  has  been  named  the  angle 
of  advance,  but,  thus  should  be  named  the  angle  between  the 
crank  arm  and  eccentric  arm  ;  for  it  represents  how  much  the 
eccentric  actually  is  in  advance  of  the  crank.  Any  other  des- 
ignation is  confusing,  and  there  is  no  valid  reason  for  any  other 
use  of  this  term.  If  there  ever  was  a  good  reason  for  it,  it 
does  not  exist  now.  In  this  book,  the  "angle  of  advance " 
means  the  angular  advance  of  the  eccentric  relative  to  the  crank, 
as  represented  by  angle  8-2,  Fig.  4  and  6. 

When,  by  continued  turning  of  the  shaft,  the  eccentric 
reaches  position  4,  the  admission  of  steam  to  the  cylinder  is 
cut  off.  Where  will  the  piston  then  be  ?  Mark  off  the  angle  of 
advance  from  point  4  in  a  reverse  direction,  and  a  radial  line 
intersecting  the  crank-Circle  marks  the  location  of  the  crank- 
pin,  and  its  horizontal  projection  will  indicate  approximately  the 
position  of  the  piston  in  the  cylinder  when  the  admission  of 
steam  is  cut  off  and  expansion  commences.  The  exact  location 


THE   COMMON  SLIDE-VALVE.  11 

of  this  point  —  the  point  of  cut-off  —  is  sometimes  required, 
and  the  angularity  of  the  connecting-rod  must  then  be  taken 
into  account.  (See  last  chapter.) 

As  steam  always  is  admitted  at  a  point  very  near  the  com- 
mencement of  the  stroke,  the  period  of  admission  must  be  made 
shorter  or  longer  according  as  an  earlier  or  later  "cut-off"  is 
required.  This  can  be  effected  by  lengthening  or  shortening 
the  steam-lap  ;  but  as  the  point  of  admission  is  fixed  near  the 
commencement  of  the  stroke,  the  period  as  a  whole  must  occur 
earlier  or  later  according  to  the  location  of  the  point  of  cut-off, 
and  the  angle  of  advance  must  be  changed  accordingly  —  which 
will  become  quite  clear  by  an  inspection  of  Fig.  4.  Thus  is 
established  the  important  rule:  Period  of  admission  is  shortened 
by  increasing  the  lap  and  the  angle  of  advance,  and  is  lengthened 
by  diminishing  the  lap  and  angle  of  advance.  Also  mark : 
that  all  periods  of  steam  distribution  occur  earlier  or  later  in  the 
stroke,  according  as  the  eccentric  is  turned  ahead  or  back  on  the 
shaft. 

VALVES    WITHOUT    LAP. 

Valves  have  been  used  without  steam-  and  exhaust-lap  at 
a  time  when  the  gain  by  expansion  was  not  fully  recognized 
and  compression  of  exhaust  had  no  significance.  When  such 
valves  have  their  eccentrics  at  right  angles  to  the  crank,  the 
points  of  admission  and  release  of  the  steam  occur  when  the 
crank  is  on  its  "  dead  center  "  ;  but  the  eccentric  was  presum- 
ably moved  forward  some  to  give  the  valve-lead.  Such  valves 
are  not  used  now,  and  they  may  be  classed  with  historical  curi- 
osities. In  treatises  on  the  steam-engine  this  lap-less  construc- 
tion is  usually  discussed  at  length  as  an  introductory  to  a  chapter 
on  slide-valves,  though  the  discussion  of  this  special  and  obsolete 
construction  seems  hardly  profitable,  and  it  is  not  conducive  to 
a  broad,  practical  conception  of  the  general  subject. 


12 


THE  SLIDE-VALVE  AND  ITS  FUNCTIONS. 


THE    PRIMITIVE    VALVE-DIAGRAM. 

Fig.  6  is  a  combination  of  diagrams  4  and  5,  and  it  represents 
a  simple  D-valve  diagram.  The  crank  is  supposed  to  be  at  its 
dead  center,  or  at  the  extremity  of  its  throw,  at  the  commence- 


19 


Fig.  6. 

ment  of  the\forward  stroke,  and  significant  positions  of  the  vajve 
during  one  revolution  of  the  crank  are  indicated  diagram  mat  ically 
to  the  left.  The  various  positions  of  the  eccentric  are  marked 
on  the  eccentric-circle  in  the  following  order.  * 

1.  Point  of  admission,  just  before  end  of  return  stroke. 

2.  Lead  at  commencement  of  forward  stroke. 

3.  Extreme  throw  of  valve,  port  wide  open. 

4.  Steam  is  cut  off,  expansion  commences. 

5.  Valve  in  central  position. 

6.  Point  of  release. 

7.  Exhaust-lead,  at  commencement  of  return  stroke. 

8.  Extreme  throw  of  valve,  exhaust  wide  open. 

9.  Exhaust-closure ;  compression  commences. 
10.  Valve  in  central  position. 

I 


. 

THE    COMMON  SLIDE-VALVE.  IS 

This  diagram  exhibits  in  a  natural  manner  all  that  is  required 
for  a  full  understanding  of  the  functions  and  principles  of  con- 
struction of  a  common  slide-valve,  and  from  it  the  position  of 
the  valve  relatively  to  the  ports,  at  any  point  of  the  stroke,  can 
readily  be  ascertained  by  marking  off  the  angle  of  advance  on 
the  eccentric-circle.  Note  that  in  this  diagram  the  eccentric- 
arm  is  supposed  to  be  moved  in  unison  with  the  crank-arm,  as 
it  does  move  in  reality. 

The  simple  and  direct  relationship  between  eccentric  and 
valve  motion,  as  here  assumed,  is  often  changed  by  the  interven- 
tion of  a  special  valve-gear ;  but  the  resolution  of  such  cases 
presents  no  special  difficulty.  Usually  the  valve-motion  is 
assumed,  and  the  throw  and  position  of  the  eccentric  are  then 
deduced  from  the  design  of  the  valve  gear. 

It  should  be  particularly  noted  that  the  valve-end  of  the 
eccentric-rod  must  be  in  the  same  position  when  the  valve  opens 
and  closes  the  port,  and  that,  therefore,  each  pair  of  points,  1-4, 
and  6-9,  which  mark  the  beginning  and  end  of  the  admission  and 
the  exhaust  period  respectively,  must  be  equally  distant  from 
a  certain  point  which  marks  the  location  of  the  eccentric-rod  pin 
when  the  valve  and  port  edges  come  together,  and  that,  there- 
fore, if  the  valve-end  of  the  eccentric-rod  travels  in  a  straight 
line,  which  extended  passes  through  the  center  of  the  crank- 
shaft, chords  1-4  and  6-9  must  be  parallel.  A  slight  devia- 
tion from  this  direction,  caused  by  the  swing  of  an  ordinary 
rocker  arm,  is  of  so  little  consequence  that  it  may  be  entirely 
ignored.* 

The  foregoing  discussion  presents  the  fundamental  princi- 
ples which  must  govern  the  construction  of  slide-valves  of  any 
description,  and  it  will  serve  as  an  introduction  to  the  study  of 
other  forms  of  valves. 

*  The  general  effect  of  a  rocker  motion  in  other  directions  than  the  center  of  the  shaft  is 
•discussed  in  the  last  chapter  of  the  book. 


14 


THE  SLIDE-VALVE   AND   ITS  FUNCTIONS. 


SWEET  S    VALVE-DIAGRAM. 

In  Fig.  6  the  various  positions  of  the  valve  relative  to  the 
port  during  a  complete  revolution  of  the  eccentric  are  indicated 
by  the  eccentric-arm,  as  a  pointer ;  but  if  the  circular  figure  be 
turned  backwards  through  an  angle  equal  to  the  angular  advance 
of  the  eccentric,  without  disturbing  the  crank,  all  the  points  in 
the  circumference  will  be  placed  in  the  same  position  relative  to 


Fig.  7- 


the  crank-arm  as  they  now  occupy  relative  to  the  eccentric-arm  ; 
and  if  then  the  crank-arm,  or  its  center  line,  be  moved  into  any 
new  position,  the  corresponding  position  of  the  valve  will  appear 
directly  from  the  marks  in  the  circumference  of  the  circle.  A 
valve-diagram  thus  modified  is  shown  in  Fig.  7.  Note  that  valve 
measurements  and  port-openings  are  taken  at  right  angles  to  the 
oblique  lines,  and  that  these  lines  must  be  parallel.  For  con- 


THE   COMMON  SLIDE-VALVE.  15 

venience,  the  eccentric-circle  is  drawn  full  size,  and  the  crank- 
circle  is  reduced,  so  as  to  make  both  circles  appear  of  same  size. 

From  this  circular  diagram  a  theoretical  indicator  diagram 
can  readily  be  constructed,  as  shown,  which  adds  greatly  to  its 
usefulness  ;  for  to  many  engineers  the  indicator  diagram  exhibits 
and  explains,  at  a  single  glance,  all  the  peculiarities  of  the  steam 
distribution  in  the  cylinder,  and  it  sometimes  contains  a  whole 
story  in  graphic  language. 

This  valve-diagram,  slightly  modified,  was  first  published  by 
Professor  John  E.  Sweet  in  the  American  Machinist  of  August 
30,  1884,  and  I  know  no  reason  why  it  should  not  be  named  the 
«  Sweet  valve-diagram. "  No  attempt  should  be  made  to  use 
the  same  diagram  to  indicate  different  valve  proportions  or  set- 
tings, for  it  makes  it  confusing  to  the  eye,  and  it  is  entirely  un- 
necessary, as  half  a  dozen  such  diagrams  can  be  drawn  in  "  less 
than  no  time." 

In  order  that  the  opening  and  closing  of  the  ports  may 
take  place  at  the  proper  moments  during  the  forward  stroke 
and  return  stroke  respectively,  the  eccentric  must  be  set  at  a 
certain  angle  in  advance  of  the  crank  ;  and  its  location  depends, 
therefore,  on  the  direction  in  which  the  crank  turns,  though  the 
angle  of  advance  is  the  same  in  either  case.  A  reversal  of  the 
crank  motion  would  change  the  valve  diagram,  only  so  far  as  all 
points  above  the  center  line  would  occupy  corresponding  posi- 
tions below  it,  and  vice  versa,  —  as  if  the  diagram  were  turned 
around  its  horizontal  diameter. 

VARIABLE    VALVE    TRAVEL. 

A  glance  at  the  diagram  shows  that  the  longer  the  lap  the 
shorter  the  period  of  admission,  and  the  smaller  the  port  open- 
ing ;  but  it  should  also  be  noted  that  the  length  of  periods  of 
admission  and  exhaust  depends  absolutely  on  the  relation  be- 
tween lap  and  travel  of  valve,  and  that,  therefore,  shortening 
the  travel  has  the  same  effect  as  increasing  the  lap,  so  far  as 


16  THE   SLIDE-VALVE   AND   ITS  FUNCTIONS. 

these  periods  are  concerned  ;  but   shorter  travel  yields  smaller 
openings  for  admission  and  release. 

It  has  been  shown  how  the  location  of  the  point  of  cut-off 
can  be  changed  by  changing  the  lap  of  the  valve  and  the  angu- 
lar advance  of  the  eccentric,  and  it  is  evident  that  this  may  also 
be  done  by  changing  the  throw  of  the  eccentric  and  its  angular 
advance,  without  changing  the  lap.  For  instance  :  by  diminish- 
ing the  throw  the  period  of  admission  becomes  less,  and  by  ad- 
vancing the  eccentric  the  proper  lead  is  obtained,  which  will 
become  clear  by  an  inspection  of  diagrams  6  and  7.  Improved 
slide-valves  are  often  driven  by  shiftable  eccentrics  whose  throw 
and  angular  advance  are  automatically  changed  so  as  to  vary  the 
point  in  the  stroke  where  steam  is  cut  off,  as,  for  instance,  on 
many  high-speed  engines  ;  or  the  same  result  is  obtained  by 
hand  adjustment,  as  on  the  locomotive. 

LIMITATIONS    OF    THE    COMBINATION    VALVE. 

The  main  limitations  of  the  D  valve,  or  combined  steam 
and  exhaust  valve,  as  a  steam  distributer,  is  due  to  the  fixed 
union  of  its  steam  and  exhaust  edges,  as  when  separate  steam 
and  exhaust  valves  are  driven  by  means  of  one  rod.  Maximum 
steam  and  exhaust  opening  must  occur  when  the  eccentric  is  at 
either  end  of  its  stroke,  just  in  the  middle  of  periods  of  admis- 
sion and  exhaust  respectively  ;  and  there  being  only  one  eccen- 
tric, this  must  occur  at  diametrically  opposite  points  in  the  period 
of  revolution.  If,  for  instance,  the  admission  period  is  fixed, 
the  exhaust  period  cannot  be  arbitrarily  changed  ;  for,  the  eccen- 
tric being  fixed  on  the  shaft  to  suit  the  admission  period,  we 
can  only  vary  the  exhaust  period  by  varying  the  exhaust  lap, 
but  this  will  give  a  variation  in  both  directions  ;  that  is,  if  the 
exhaust  opens  earlier  it  will  close  later,  and  if  it  opens  later  it 
will  close  earlier.  The  cycle  of  contiguous  events,  as  marked 
on  the  eccentric  circle,  shows  this  clearly  ;  also  that  an  early 
cut-off  of  the  steam  in  the  cylinder  is  followed  by  early  release 


THE   COMMON  SLIDE-VALVE.  17 

and  early  exhaust  closure,  and  consequently  by  much  compres- 
sion of  the  exhaust.  It  is  therefore  quite  common  practice, 
when  not  exhausting  into  a  condenser,  to  omit  the  exhaust  lap. 
Moving  the  exhaust  edge  back  still  farther  would  probably  give 
too  early -release.  .  „ 

It  should  be  noted  that  the  functional  restrictions  here  men- 
tioned are  inherent  in  any  combination  of  a  steam  and  exhaust 
valve  conjunctively  driven  by  a  single  eccentric,  because  such 
valve-gear  must  derive  all  its  motions  from  the  eccentric,  and 
its  alternations  must  follow  closely  those  of  the  engine,  without 
reference  to  the  nature  of  the  valve-gear. 

The  increased  compression  which  follows  an  early  cut-off 
is  sometimes  considered  an  unavoidable  evil  or  inherent  defect, 
and  sometimes  a  desirable  feature  or  incidental  advantage  of 
the  combination  slide-valve,  according  to  existing  conditions  or 
various  theories. 

It  should  be  noted  that  by  an  early  cut-off  the  steam  open- 
ing is  much  restricted,  and  particularly  so  near  the  point  of 
cut-off,  where  the  steam  current  is  comparatively  rapid.  The 
most  natural  remedy  would  be  an  increase  of  the  valve  travel, 
but  in  case  of  an  unbalanced  valve  this  would  increase  the 
unbalanced  area  and  the  friction  proportionally.  When  it  is 
desired  to  limit  the  valve  travel,  duplicate  or  supplementary 
steam-ports  are  sometimes  resorted  to.  The  restriction  of  the 
port-opening,  however,  is  of  little  consequence,  unless  the  steam 
is  cut  off  very  early  in  the  stroke ;  and  the  attendant  early  re- 
lease is  probably  the  most  objectionable  feature.  Very  early 
cut-off  is  only  used  in  connection  with  a  shiftable  eccentric  or 
with  a  link-gear  ;  and  the  discussion  of  this  case  will  be  resumed 
later. 

The  central  exhaust  cavity  of  the  D-valve  removes  pressure 
from  the  front  of  the  valve,  and  causes  it  to  be  held  firmly  to 
its  seat  by  steam  pressure  on  its  back ;  but  the  unbalanced 
pressure  is  always  excessive,  and  in  order  to  reduce  it  a 


18  THE  SLIDE-VALVE   AND  ITS  FUNCTIONS. 

pressure-balancing  device  on  the   back  of  the  valve   is    often 
resorted  to.* 

On  long-stroke  engines  the  steam  passages  become  very 
long  unless  the  valve  is  lengthened  correspondingly,  and  the  ex- 
haust passage  between  the  valve  and  cylinder  makes  it  impossi- 
ble to  bring  the  valve  very  close  to  the  cylinder-bore  ;  but  these 
objections  are  only  of  consequence  when  it  is  desired  to  make 
the  steam  passages  short  and  direct.  Great  adaptability,  sim- 
plicity, and  compactness  are  characteristics  of  the  common  D- 
valve  ;  and  for  engines  using  steam  at  low  or  medium  pressure 
governed  by  throttling,  it  will  hardly  be  superseded. 

STEAM-PORTS. 

When  designing  slide-valves,  one  of  the  first  data  required 
is  the  size  of  steam-ports.  No  general  rule  can  be  given  for 
this ;  in  fact,  progressive  engineers  consider  it  an  unsettled 
matter.  Much  depends  on  the  piston  speed,  but  there  are 
other  influential  conditions.  If  it  is  desired  to  admit  steam 
to  the  cylinder  under  full  pressure,  larger  ports  are  required 
than  if  the  pressure  is  to  be  throttled  down  ;  and  if  a  consider- 
able decrease  of  speed  is  permissible  under  an  occasional  extra 
heavy  load,  as,  for  instance,  by  hoisting-engines,  comparatively 
small  ports  give  entire  satisfaction,  and  are  preferable  to  larger 
ones.  The  length  and  shape  of  steam  passage  and  port  may 
have  an  important  bearing  on  their  sectional  area,  but  narrow 
ports  are  requisite  in  order  to  keep  the  valve  motion  within 
practical  limits.  The  discovery  may  still  be  made  that  the  pas- 
sage, and  not  the  port,  is  the  governing  element.  The  "me- 
chanical instinct  "  of  the  engine-builder  will  make  the  port 
conform  to  the  passage,  but  this  instinct  is  not  reliable  when 
the  molecular  action  of  steam  is  involved.  In  the  writer's  per- 
sonal experience,  for  instance,  an  abrupt  contraction  of  the  port 
to  less  than  half  its  original  size,  as  shown  in  Fig.  8,  did  not 

*  See  page   42. 


t 

THE    COMMON  SLIDE-VALrE.  19 

lower  the  admission-line  or  raise  the  exhaust-line  on  the  indica- 
tor-card. This  phenomenon  is  susceptible  of  a  rational  expla- 
nation, but  mere  speculation  is  not  in  place  here. 

Incidental  experiences  seem  to  prove  that  the  condition  of 
the  steam,  whether  wet,  dry,  or  superheated,  is  of  no  little 
consequence.  Dry  steam,  being  more  subtile 
than  wet  steamy  moves  easier  or  does  not  adhere 
to  the  sides,  and  therefore  does  not  require  so 
large  ports  or  passages.  FiS-  8- 

It  may  safely  be  assumed,  that  if  the  ports  and  passages  are 
large  enough  to  allow  the  exhaust  to  pass  through  without  appre- 
ciable back  pressure,  they  are  amply  large  for  the  entering 
steam,  and  if  the  indicator  card  shows  a  "good"  exhaust-line, 
the  ports  are  large  enough,  no  matter  how  bad  the  "steam-line  " 
appears. 

For  some  years  past  it  has  been  a  rule  to  make  the  ports  of 
high-speed  engines  large  enough  to  make  the  mean  velocity  of 
the  steam  current  6,000  feet  per  minute,  which  for  600  feet 
piston  speed  makes  the  port  area  equal  to  one-tenth  of  the 
piston  area  ;  but  occasional  experiences  indicate  that,  if  the  pas- 
sages are  short,  a  much  smaller  area  may  give  perfect  satis- 
faction, and  the  above  rule  is  probably  now  becoming  obsolete. 

The  rule  here  mentioned  entirely  ignores  friction  against 
the  walls  of  the  passage  ;  this  could  be  remedied  by  introducing 
some  power  of  the  diameter  of  the  cylinder  as  a  separate  factor 
in  the  formula.  The  general  formula  might,  for  instance,  be : 
Velocity  of  steam,  in  feet  per  minute,  equals  3,000  times  the 
cube  root  of  the  diameter  in  inches.  For  an  8-inch  cylinder  this 
would  make  the  mean  velocity  through  the  ports  6,000  feet  per 
minute,  and  for  a  2/-inch  cylinder  it  would  make  it  9,000  feet. 

PORT-OPENING. 

"  Port-opening  "  means  the  uncovered  part  of  the  port,  and  it 
should  not  be  confounded  with  the  "  port,"  which  is  the  orifice 


20  THE   SLIDE-VALVE   AND   ITS  FUNCTIONS. 

of  the  steam  passage.  The  valve  may  not  open  for  steam  as 
much  as  the  width  of  the  port ;  for  experience  has  taught  that 
restriction  of  a  steam  passage  by  two  sharp  edges,  within  a  cer- 
tain limit,  has  very  little,  if  any,  effect  on  the  steam  current. 
It  is  known,  for  instance,  that  a  throttling-valve  of  the  piston 
type  does  not  have  to  open  but  very  little  to  allow  full  pressure 
steam  to  pass  through,  and  on  many  automatic  cut-off  engines, 
the  port  opening  is  much  restricted  without  appreciable  loss  of 
pressure. 

VALVE    DIMENSIONS. 

After  the  travel,  point  of  cut-off,  and  lead  have  been  deter- 
mined upon,  a  circular  diagram  like  Fig.  7  may  be  drawn,  and 
this  will  give  the  lap  and  port  opening.  If  a  larger  port-open- 
ing is  desired  the  lap  and  travel  must  be  increased  proportion- 
ally. A  line  may  be  drawn  obliquely  across  the  parallel  lines 
as  shown,  so  as  to  give  the  desired  port -opening,  and  the  other 
dimensions  will  appear  at  once,  correctly  proportioned,  on  the 
same  line.  By  this  method  the  lead  will  be  increased  with  the 
port-opening,  but  the  period  of  preadmission  remains  unaltered. 
In  any  case,  it  is  advisable  to  draw  a  fresh  diagram  for  any  con- 
templated alteration,  for  the  labor  it  involves  is  very  insignifi- 
cant compared  with  resulting  clearness  and  simplicity  ;  and  the 
final  diagram  should  be  duly  labeled  and  kept  as  a  record  for 
future  reference. 

After  port,  travel,  steam-  and  exhaust-lap  have  been  obtained, 
a  section  of  valve  and  valve-seat  may  be  drawn  ;  and  it  should 
be  observed  that  the  exhaust  after  leaving  the  port  is  not  inter- 
fered with  too  much  by  the  opposite  exhaust  edges.  On  unbal- 
anced valves  it  is  advisable  to  reduce  the  exhaust  cavity  as  much 
as  possible  ;  and  in  that  case,  the  central  exhaust  opening  at  the 
extreme  of  the  travel  may  be  reduced  to  five-eighths  of  the  area 
of  the  steam-port  by  overlapping  of  the  valve. 


THE   COMMON  SLIDE-VALVE, 


21 


VALVE    DIAGRAM    FOR    SHIFTING-ECCENTRIC    ENGINES. 

By  making  the  parallel  lines  in  Fig.  7  slant  the  other  way, 
as  if  the  figure  were  turned  end  for  end,  we  get  a  diagram  which 
has  a  certain  constructive  advantage  and  also  a  less  desirable 
feature.  It  becomes  a  left-hand  diagram  for  a  right-hand  crank 
motion,  as  it  were  ;  and  the  various  valve  movements,  incidental 
to  the  turning  of  the  crank,  must  be  traced  out  from  right  to 
left,  while  the  crank  actually  turns  from  left  to  right.  But  such 
diagram  will  present  the  slanting  lines  at  right  angles  to  the 
eccentric  arm,  which  facilitates  its  construction  for  valves  with 
variable  travel,  as  used  on  certain  automatic  cut-off  engines  and 
on  locomotives  and  marine  engines. 

Fig.  9  shows  how  to  lay  out  a  valve  diagram  in  this  manner 
for  an  engine  having  two  valves  driven  by  separate  eccentrics, 
one  of  which  controls  the 
steam  admission  and  the 
other  controls  the  exhaust. 
The  induction-valve  is  driven 
by  an  eccentric  of  variable 
throw,  the  center  of  which  is 
supposed  movable,  relative  to 
the  crank,  on  the  curved  path 
ABC,  whereby  its  throw  and 
angular  advance  are  simul- 
taneously changed.  Thus, 
when  the  period  of  admission 
is  shortened  by  reducing  the 
throw,  the  proper  lead  is  main- 
tained by  a  corresponding 
angular  advance.  In  the  nat- 
ural diagram,  Fig.  6,  lead  is 


"Exh.  Ecc. 


Fig.  9.     Sweet's  Valve  Diagram. 


represented  by  the  horizontal  distance  of  the  center  of  eccentric 
from  chord  1-4,  and  it  can  readily  be  reproduced  in  Fig.  9  in 


22  THE   SLIDE-VALVE   AA'D   77 S  FUNCTIONS. 

the  following  manner :  With  a  radius  equal  to  the  lap  draw  a 
circle,  as  shown,  and  drop  a  vertical  from  center  of  eccentric ; 
the  distance  from  this  to  the  lap  circle  is  lead.  In  the  present 
case,  the  lead  becomes  less  as  the  eccentric  advances,  and  is  nil 
at  C,  opposite  the  crank.  When  the  eccentric  is  at  full  throw, 
the  diagram  becomes  an  exact  counterpart  of  Fig.  7  in  a  re- 
versed position  ;  but  suppose  the  valve  were  to  cut  off  steam  at 
one-quarter  of  the  piston-stroke,  without  changing  its  travel, 
then  the  chord  1-4  would  become  short  and  steep,  as  shown, 
and  the  eccentric  would  be  advanced  to  a  position  at  right  angles 
to  this  chord,  and  the  lap  would  have  to  be  increased,  as  repre- 
sented by  the  increased  distance  of  the  chord  from  the  center. 
But  as  the  lap  of  the  valve  cannot  vary,  its  travel  must  be  re- 
duced in  order  to  obtain  the  requisite  proportion  between  lap 
and  travel ;  and  this  is  effected  by  moving  the  eccentric  from  A 
to  point  B,  where  a  tangent  to  the  lap  circle,  at  right  angles  to 
the  eccentric-arm,  will  cut  off  an  arc  of  the  reduced  circle  of 
rotation  through  B,  which  arc,  or  its  center  angle,  represents 
period  of  admission  within  the  prescribed  limits  for  one-quarter 
of  the  piston-stroke.  The  small  shaded  segment  shows  the 
port-opening,  which  is  remarkably  small  considering  that  such 
engines  often  carry  full  load  when  the  valve  is  cutting  off  at 
that  point  in  the  stroke. 

It  should  be  noted  that  the  velocity  of  the  piston  varies  — 
it  is  greatest  at  mid-stroke  and  becomes  nil  at  the  ends  —  and 
that  the  efficiency  of  the  port-opening  depends  on  the  local 
speed  of  the  piston.  For  this  reason  only  a  very  small  opening 
is  required  for  admission  of  steam  at  the  beginning  of  the 
stroke ;  but  at  one-quarter  of  the  stroke  the  piston-speed  has 
greatly  increased,  and  in  order  to  get  a  good  "  steam-line  "  and 
a  "square  cut-off"  there  should  be  ample  steam-opening  near 
the  point  of  cut-off.  Fig.  9  shows  clearly  how  unfavorable  the 
conditions  are  for  a  square  cut-off  early  in  the  stroke  of  single- 
valve  "automatic  engines"  and  locomotives,  and  how  incom- 


THE    COMMON  SLIDE-VALVE.  23 

parably  better  the  conditions  become  by  later  cut-off.  An  early 
cut-off  by  a  single  valve  must,  in  any  event,  reduce  the  port- 
opening  considerably  on  account  of  the  long  lap  required  ;  but 
by  automatic  or  adjustable  cut-off,  it  becomes  still  smaller,  on 
account  of  the  reduced  valve  travel.  It  is  also  worthy  of  notice 
that  the  rapidity  of  the  valve  action  is  less  by  early  cut-off, 
because  this  occurs  when  the  eccentric  is  near  the  extreme  of 
its  travel,  where  its  lateral  motion  is  comparatively  slow.  The 
port  opening,  when  steam  follows  one-quarter  of  the  stroke  is,  in 
the  case  here  considered,  about  one-sixth  of  the  maximum  open- 
ing, or  about  three-sixteenths  of  an  inch  for  a  1 2-inch  cylinder. 

The  exhaust  eccentric  is  supposed  to  be  fixed  on  the  shaft, 
giving  a  constant  valve  travel  and  fixed  points  of  release  and 
exhaust  closure,  as  in  Fig.  7.  With  direct  valve  connection  and 
exhaust  escaping  over  the  inside  port  edges,  the  exhaust  eccen- 
tric would  be  in  position  A ;  but  in  the  case  under  considera- 
tion, the  exhaust  is  supposed  to  take  place  over  the  outside  edges 
of  the  ports,  and  the  eccentric  will,  therefore,  be  at  point  8, 
diametrically  opposite  point  A. 

If  steam  and  exhaust  valves  were  driven  by  one  eccentric, 
the  slanting  lines  in  the  diagram  would  be  parallel,  and  when 
steam  is  cut  off  at  one-quarter  stroke,  the  exhaust  opening  and 
closure  would  be  at  O  and  N  respectively ;  which  means  prema- 
ture release  and  much  compression.  By  using  two  eccentrics 
the  early  release  is  avoided,  and  the  compression,  being  con- 
stant, is  better  adapted  to  promote  smooth  running  under  all 
conditions.  Lap  may  be  used  to  advantage  on  a  separate  ex- 
haust-valve. 

Note  that  in  this  diagram  the  slanting  lines  are,  as  a  rule, 
not  parallel. 

It  should  also  be  noted  that  the  opening  for  exhaust  is  al- 
ways ample,  and  takes  place  when  the  eccentric  is  at  or  near  its 
half-throw,  and  that,  therefore,  an  early  release  is  not  required. 

As  here  represented,  the  fixed  travel  of  the  exhaust -valve  is 


24  THE  SLIDE-VALVE   AND  ITS  FUNCTIONS. 

equal  to  the  maximum  travel  of  the  steam-valve  ;  but  this  is 
evidently  not  necessary,  as  a  much  shorter  travel  of  the  exhaust- 
valve  would  give  ample  opening  for  release.  When  a  single 
valve  controls  both  steam  and  exhaust,  the  exhaust  lap  is  usu- 
ally omitted ;  and  though  the  exhaust  opening  is  much  reduced 
by  the  reduced  throw,  it  is  still  ample  when  steam  is  cut  off  at 
one-quarter  of  the  stroke ;  and  as  the  exhaust  lead  is  nearly 
constant,  the  very  early  release  must  be  detrimental  to  steam 
economy. 

The  ideal  indicator  diagram,  annexed  to  Fig.  9,  illustrates 
the  action  of  an  automatic  admission  and  cut-off  valve  in  combi- 
nation with  a  separate  exhaust-valve,  and  dotted  lines  show  the 
corresponding  action  of  a  single  combination-valve,  the  point  of 
cut-off  in  both  cases  being  at  one-quarter  of  the  piston-stroke. 

If  preferred,  the  diagram  Fig.  7  may  be  used  for  shiftable 
eccentrics.  It  will  only  be  necessary  to  draw  the  shifting-path 
of  the  eccentric  on  the  other  side  of  the  center,  where  it  is  to 
be  considered  as  a  construction  line  only. 

VARIATION    IN    PORT-OPENING. 

Diagram  10  represents  variation  in  port -opening.  When 
steam  is  cut  off  at  one-quarter  of  the  piston -stroke,  the  variation 
is  represented  by  consecutive  ordinates  in  the  shaded  areas,  and 
the  light  areas  show  the  variation  when  steam  is  cut  off  a  little 
before  three-quarters  of  the  stroke.  Admission  and  exhaust 
are  here  supposed  to  be  controlled  by  a  single  valve,  and  the 
exhaust-opening  is  represented  by  ordinates  to  the  lower  curve. 
Ordinates  to  the  crank-circle  represent  —  on  the  proper  scale  — 
velocity  of  the  piston,  and  it  will  be  noticed  that  at  one-quarter 
stroke  it  has  nearly  attained  its  maximum  velocity. 

For  a  given  point  of  cut-off,  a  certain  relation  exists  between 
lap  and  travel,  and  for  earlier  cut-offs  the  lap  becomes  greater, 
or  else  the  travel  becomes  less.  If  the  lap  for  a  given  cut-off 
is  increased,  the  travel  must  increase  at  the  same  rate  or  nearly 


THE    COMMON  SLIDE-VALVE. 


25 


so  ;  and  the  port-opening,  bearing  a  fixed  relation  to  the  lap  and 
travel,  is  increased  proportionally.  Hence,  by  increasing  the 
lap  of  a  valve  of  variable  travel,  the  port -opening  is  also  in- 
creased ;  but  the  increased  lap  curtails  the  range  of  cut-off,  for 
the  latest  cut-off  is  determined  by  the  relation  of  lap  to  maxi- 
mum travel.  In  this  connection  it  is  sometimes  stated  that  the 
port-opening  is  proportional  to 
the  lap,  which  is  absolutely  true 
only  if  the  lead  is  zero,  or  if  it  is 
directly  proportional  to  the  travel. 
A  wide  range  of  power  is 
often  desired  in  automatic  cut-off 
engines,  25  to  35  per  cent  above 
the  rated  or  economical  load  is 
specified,  and  the  valve  and  gov- 
ernor must  be  designed  to  meet 
this  requirement.  An  extreme 
cut-off  at  three-quarters  of  the 
stroke  is  sometimes  imperative  ;  FiS-  I0- 

but  at  the  same  time,  it  should  be  kept  in  mind  that  there  is  a 
certain  desirable  or  practical  limit  to  the  travel  of  the  valve,  and 
that  by  extending  the  range  of  cut-off  the  port-opening  *  for 
earlier  cut-offs  becomes  smaller.  Let  the  travel  be  four  inches, 
and  let  the  latest  cut-off  be  at  three-quarters  of  the  stroke,  then 
when  cutting  off  at  one-quarter  stroke,  the  port-opening  is  about 
three-sixteenths  of  an  inch ;  but  if  latest  cut-off  is  at  five-eighths 
of  the  stroke,  the  port-opening  for  one-quarter  stroke  becomes 
about  one-quarter  of  an  inch  ;  and  making  one-half  the  stroke, 
the  limit  for  cut-off  increases  the  port-opening  for  one-quarter 
stroke  to  five-sixteenths  of  an  inch. 

NOTES    ABOUT     LEAD. 

It  used  to  be  general  practice  to  give  the  valve  a  constant 
lead,  irrespective  of  the  point  of  cut-off ;   but  the  theory  in  sup- 


26  THE  SLIDE-VALVE   AND   ITS  FUNCTIONS. 

port  of  this  practice  is  now  fast  becoming  obsolete,  and  later 
experience  has  established  the  fact  that  the  lead  may  vary  con- 
siderably without  detriment  to  smooth  running. 

Lead  means  width  of  port-opening  at  commencement  of  the 
stroke  ;  and  no  reference  is  made  to  the  period  of  lead  or  lead 
angle,  as  represented  by  arc  1-2,  or  by  the  intercepted  angle, 
though  it  seems  quite  proper  to  take  this  —  the  time  element  — 
in  account.  Assuming  a  constant  lead,  the  lead  period  will  vary 
according  to  the  location  of  the  point  of  cut-off.  By  earlier  cut- 
off the  steam  is  admitted  earlier  to  the  cylinder,  and  it  has  con- 
sequently more  time  to  fill  the  clearance  spaces  ;  it  will  be  more 
effective  on  that  account,  and  it  can  hardly  be  disputed  that  this 
is  of  as  much  consequence  as  the  extent  of  port-opening  at  the 
end  of  the  return  stroke  —  or  perhaps  more  so. 

If  in  Fig.  9,  the  path  ABC  is  made  straight  and  perpendicu- 
lar, the  lead  will  be  constant  ;  and  any  desired  variation  in  lead 
may  evidently  be  obtained  by  making  the  eccentric  shiftable  in 
other  directions,  more  or  less  deviating  from  the  perpendicular. 
In  the  particular  case  represented  in  Fig.  9,  the  lead  decreases 
to  nothing  at  the  point  of  minimum  throw,  and  when  the  eccen- 
tric is  near  this  point,  the  port-opening  becomes  exceedingly  small; 
but  if  the  valve  has  some  lead  at  this  point,  it  will  become  the 
minimum  port-opening,  and  it  would  make  a  comparatively  large 
addition  to  the  port-opening  by  very  early  cut-off,  and  less  "  wire- 
drawing "  of  the  steam  would  probably  be  the  result ;  but 
according  to  later  theories,  wire-drawing  under  these  conditions 
is  beneficial ;  for,  by  lowering  the  initial  steam  pressure,  and  by 
rendering  somewhat  drier  steam,  it  reduces  the  initial  condensa- 
tion in  the  cylinder ;  and  it  is  claimed  that  in  case  of  a  single- 
valve  engine  early  admission  is  unnecessary  in  any  event,  because 
an  early  exhaust  closure,  incidental  to  early  cut-off,  fills  the 
clearance  space  with  compressed  exhaust  steam. 

It  is  also  easily  proven  that  by  curtailing  the  lead,  the  angu- 
lar advance  is  diminished,  and  release  and  exhaust  closure  occur 
correspondingly  later  in  the  stroke. 


THE   COMMON  SLIDE-VALVE.  27 

Negative  lead  in  conjunction  with  short  cut-off  has  the  un- 
doubted practical  advantage  that  it  will  always*  insure  perfect 
control  of  the  speed  of  the  engine  when  running  light,  whether 
the  valve  is  set  exactly  central  or  not ;  and  it  becomes  a  particu- 
larly useful  expedient  when  the  engine  is  connected  with  a  con- 
denser. 

If  there  be  any  positive  lead,  the  clearance  space  will  fill  with 
full-pressure  steam  before  the  commencement  of  the  stroke,  and 
the  expansion  of  this  steam  may  run  the  engine  if  the  back  pressure 
is  light.  Much  depends  on  the  clearance  space.  Let  it  be  8 
per  cent  of  the  piston  displacement,  and  let  the  initial  absolute 
pressure  be  1 1 5  pounds  per  square  inch  ;  then  the  absolute  mean 
pressure  during  expansion  of  the  clearance  steam  will  be  23 
pounds ;  but,  if  the  clearance  were  4  per  cent  of  the  displace- 
ment, the  absolute  mean  pressure  would  be  15  pounds  only. 
The  frictional  load  is  a  variable  or  unknown  quantity,  and  it 
may  be  very  small  when  the  engine  is  directly  connected  with  a 
dynamo.  With  atmospheric  back  pressure  and  heavy  compres- 
sion there  is  little  danger  of  the  engine  "running  away,"  but 
when  condensing  the  conditions  are  quite  different. 

COMPRESSION. 

It  should  be  noted  that  the  height  of  the  compression  curve 
varies  inversely  as  the  clearance,  and  that,  therefore,  early  ex- 
haust closure  is  compatible  with  a  large  clearance  space,  while  it 
may  be  objectionable  in  connection  with  small  clearance. 

In  single-valve  engines  and  locomotives  the  work  done  in 
the  cylinder  is  partly  regulated  by  the  variable  compression,  and 
the  variation  of  the  point  of  cut-off  is  therefore  less  than  where 
a  fixed  eccentric  governs  the  exhaust,  and  the  excessive  wire- 
drawing of  steam  incidental  to  very  early  cut-off  is  thereby  partly 
avoided.  Otherwise  there  is  nothing  gained  by  variable  com- 
pression ;  for,  according  to  D.  K.  Clark,  the  absolute  loss  by  ini- 
tial condensation  is  nearly  constant  for  all  points  of  cut-off  up  to 


28  THE   SLIDE-VALVE   AND   ITS  FUNCTIONS. 

•35  per  cent  of  the  stroke ;  and  the  ratio  of  useful'work  to  waste, 
or  the  cylinder  efficiency  at  early  cut-off,  depends  therefore  en- 
tirely on  the  work  done  per  stroke  of  engine,  irrespective  of  the 
point  of  cut-off. 

The  height  of  the  compression  curve  in  the  indicator  diagram 
depends  on  the  point  where  compression  commences,  on  the 
clearance  space,  and  on  the  absolute  back  pressure  or  density  of 
the  exhaust  —  the  greater  the  back  pressure,  the  higher  the  curve. 
And  as  it  may  reasonably  be  assumed  that  the  most  economical 
compression  is  that  which  fills  the  clearance  space  with  steam  of 
nearly  same  density  as  the  entering  steam,  the  pressure  of  this 
should  also  be  taken  into  account. 

From  this  point  of  view  it  appears  that  under  certain  condi- 
tions the  single  combination  valve  may  become  the  ideal  valve, 
and  that  such  conditions  may  exist  in  the  high-pressure  cylinder 
of  certain  compound  engines,  where  the  receiver  or  back  press- 
ure varies  according  to  the  point  of  cut-off,  being  greatest  with 
late  cut-off  and  ]ate  exhaust  closure,  and  diminishing  as  the 
point  of  cut-off  and  exhaust  closure  advances ;  for  this  may, 
under  the  conditions  imposed  by  a  single  combination  valve, 
lead  to  a  nearly  fixed  ^condition  of  density  of  the  compressed 
steam. 

Judging  from  the  above  remarks,  it  will  readily  be  agreed  that 
a  fixed  rule  for  the  determination  of  travel,  lap,  lead  and  port- 
opening  may  become  worse  than  useless  on  account  of  our  de- 
ficient knowledge  of  what  is  required  for  best  economy,  and  that 
a  wide  scope  may  be  given  to  practical  considerations. 

THE    MOTION    OF    LOCOMOTIVE    VALVES. 

To  construct  a  locomotive  valve  diagram,  it  is  only  necessary 
to  substitute  for  the  link-gear  an  equivalent  single  shiftable  ec- 
centric ;  that  is,  to  find  the  path  of  the  center  of  a  shiftable 
eccentric  which  will  produce  the  same  valve-motion  as  does  the 
link. 


THE    COMMON  SLIDE-VALVE.  '29 

Fig.  1 1  represents  diagramatically  the  chief  mechanism  of 
a  stationary  link  at  mid-gear,  and  the  positions  of  crank  and 
eccentric  centers  are  indicated.  The  virtual  angle  of  advance, 
which  should  be  used  in  the  valve  diagram,  is  a  little  greater 
than  the  actual  angle ;  and  the  diagram  shows  how  to  obtain  it. 


The  lead  is  constant,  and  the  straight  line  ACA  represent*  tho 
path  of  the  equivalent  shifting-eccentric  ;  but  the  distance  AC 
is  sufficient  for  the  valve  diagram. 

Diagrams  12  and  13  represent  "  shifting-links  "  with  "open" 
and  "crossed"  rods  respectively.     The  valve   is  supposed   to 


30  THE   SLIDE-VALVE   AND   ITS  FUNCTIONS. 

be  moved  by  a  counter-arm  rocker,  which  is  not  shown  ;  and 
this  requires  the  eccentrics  to  be  placed  on  the  crank-side 
of  the  shaft,  or  diametrically  opposite  the  position  they  would 
take  if  there  were  no  intermedial  reversal  of  the  link  motion. 
In  full  gear  the  motion  is  supposed  to  be  governed  entirely  by 
one  of  the  eccentrics,  that  is,  when  the  throw  of  the  link-block 
equals  the  throw  of  the  eccentric ;  but  in  mid-gear  the  motion  is 
governed  by  the  two  eccentrics  jointly,  and  if  the  angularity  of 
the  rods  were  the  same  for  both  dead-center  positions  of  the 
crank,  the  mid-gear  throw  would  be  exactly  as  that  of  a  single 
eccentric  located  at  the  center  of  a  straight  line  joining  the  two 
eccentric  centers,  and  the  lead  of  the  valve  would  be  constant 
for  the  entire  range  of  cut-off.  But,  owing  to  the  fact  that  the 
angularity  of  the  rods  is  not  the  same  on  both  centers,  the  mid- 
gear  valve  motion  will  be  increased  with  open  rods  and  dimin- 
ished with  crossed  rods,  and  the  mid-gear  lead  will  be  increased 
or  diminished  proportionally.  The  shifting-path  of  the  single 
equivalent  eccentric  will,  therefore,  be  curved  as  shown  in  the 
figures. 

If  it  is  desired  to  equalize  the  lead  for  both  ends  of  the 
cylinder,  the  link  must  conform  to  a  certain  curve  ;  and  any 
variation  from  this  curve  will  make  the  lead  unequal  for  back 
and  forward  centers  for  all  points  of  cut-off  but  one,  and  this 
point  may  be  fixed  at  will  by  lengthening  or  shortening  the 
valve-stem  connection. 

How  to  lay  down  the  shifting-path  of  the  equivalent  single 
eccentric  is  shown  in  the  diagram,  and  it  is  also  shown  how  to 
locate  the  central  point  in  the  link  arc,  so  as  to  give  uniformly 
equal  lead  at  both  cylinders  ends.  The  letter  A  denotes  a  cer- 
tain distance  or  unit  measurement,  and  its  designation  in  the 
figures  makes  any  textual  explanation  unnecessary.  The  eccen- 
tric-rod is  supposed  to  be  directly  in  line  with  the  rocker-pin  in 
two  full-gear  positions. 

The  rocking  motion  of  the  link  may  cause  a  marked  dis- 


THE    COMMON  SLIDE-VALVE.  31 

placement  of  the  point  of  cut-off,  if  the  link  and  saddle  pins  are 
not  properly  located ;  but  as  this  involves  the  valve-gear  only, 
it  will  not  be  discussed  here. 

The  shifting-link  with  open  rods  is  most  commonly  used  on 
American  locomotives ;  and  it  is  noteworthy  that  -this  gear  pro- 
vides maximum  lead  in  combination  with  early  cut-off,  which  is 
the  reverse  of  stationary  engine  practice.  The  heavy  compres- 
sion in  mid-gear  may  reverse  the  strains  gradually,  while,  with 
light  compression  in  full  gear,  and  at  slower  speed,  excessive 
lead  may  cause  a  violent  reversal  of  the  strains. 

Variable  lead  is  unavoidable  with  the  shifting-link,  but  the 
lead  may  be  reduced  to  any  extent  and  made  partly  negative  by 
providing  sufficient  lap  or  by  moving  the  eccentrics  back. 

MULTIPORTING. 

After  Corliss  had  established  the  superior  economy  of  early 
cut-off,  and  by  his  peculiar  valve-gear  had  produced  a  nearly 
sharp  cut-off  at  moderate  speed,  it  became  almost  an  axiom  that 
a  sharp  cut-off  is  essential  for  best  economy ;  and  it  has  appar- 
rently  been  the  object  of  engine-builders,  ever  since,  to  produce 
an  indicator-diagram  with  "square  cut-off" — which  means  a 
nearly  horizontal  "steam-line"  terminating  abruptly  where  it 
joins  the  expansion  line. 

The  slanting  steam-line  and  round  corner  is  the  result  of 
"wire-drawing,"  which  is  another  name  for  free  expansion;  but 
it  is  also  due  to  the  working  expansion  of  the  steam  already  in 
the  cylinder.  While  the  free  expansion,  in  one  sense,  represents 
a  direct  loss,  it  may,  at  the  same  time,  have  a  beneficial  effect, 
if  the  steam  is  not  absolutely  dry;  and  it  is,  therefore,  just 
possible  that  the  slanting  steam-line  and  the  round  corner  does 
not  represent  any  actual  loss. 

No  actual  knowledge,  however,  can  result  from  mere  reasoning 
in  this  case  ;  but  the  question  might  be  settled  by  careful  test- 
ing, which  to  the  writer's  knowledge  has  never  been  attempted. 


32  THE   SLIDE-VALVE   AND   ITS  FUNCTIONS. 

In  order  to  obtain  sufficient  port-opening  with  reduced 
travel,  many  valves  have  one  or  two  supplementary  steam-pas- 
sages, which  communicate  with  each  steam-port  and  into  which 
steam  is  admitted  over  special  steam  edges,  which  open  and  close 
for  steam  admission  simultaneous  with  the  main  steam  edges. 

How  much  this  actually  improves  the  steam-line  on  the 
indicator  card  has  probably  never  been  fully  investigated,  or 
experimental  results  have  not  been  published.  Such  experi- 
menting would  be  extremely  simple  ;  for  the  supplementary  ports 
in  the  valve  could  easily  be  temporarily  blocked,  and  it  may 
have  been  tried  in  some  university  laboratory. 

Common  sense  suggests  that  two  port-openings  will  give  a 
better  steam-line  and  sharper  cut-off  than  one  opening,  but 
nothing  definite  is  known  about  it.  Many  incidents  in  steam- 
engine  practice  may  be  accounted  for  by  the  hypothesis  that  a 
sharp  local  obstruction  in  the  steam-passage  has  an  almost  im- 
perceptible effect,  until  the  free  opening  has  been  reduced  to  a 
certain  extent,  after  which  a  rapid  decrease  in  the  flow  follows  ; 
and  if  that  be  so,  the  next  pertinent  question  is :  How  much 
may  the  opening  be  reduced  before  this  critical  point  is  reached  ? 

In  this  connection,  the  fact  should  be  recognized  that  the 
indicator  diagram  is  not  a  reliable  criterion  on  steam  economy ; 
also  that  a  valve  which  will  stay  comparatively  tight  is  a  require- 
ment of  prime  importance,  for  whatever  the  loss  or  gain  by 
wire-drawing,  compression,  release,  etc.,  the  peculiar  steam  dis- 
tribution due  to  leaking  of  the  valve  can  under  no  circumstances 
be  profitable ;  and  as  a  multiplication  of  the  port-openings  may 
increase  the  inevitable  leakage  loss,  it  is  quite  evident  that  if  no 
objection  could  be  raised  to  the  round  corner  and  slanting  steam- 
line  on  the  indicator  card,  many  valves  would  be  reconstructed. 

SETTING  THE  ENGINE  ON  DEAD  CENTERS. 

When  the  piston  is  at  the  end  of  its  stroke,  and  the  connect- 
ing-rod is  right  on  the  center  line  of  the  engine,  in  line  with 


THE    COMMON  SLIDE-VALVE.  33 

the  crank-shaft,  then  no  amount  of  steam  pressure  will  put  the 
crank  in  motion,  and  the  engine  is  therefore  said  to  be  on  its 
dead  center.  When  near  the  dead  point  the  piston-motion 
becomes  very  slow,  and  it  is  actually  reduced  to  nothing  at  the 
moment  when  the  motion  is  reversed.  Near  the  end  of  the 
stroke  the  crank-motion  is  nearly  at  right  angle  to  the  piston- 
motion,  and  it  becomes  actually  so  at  the  moment  the  crank 
passes  the  center  line.  At,  or  near,  this  point  there  is  very 
little  motion  of  the  cross-head  —  it  becomes  nearly  stationary  — 
and  it  is,  therefore,  very  difficult  to  determine  the  dead  center 
position  of  the  crank  by  observing  the  motion  of  the  cross-head. 
On  the  other  hand,  the  eccentric  is  not  far  from  mid-throw  ; 
and  the  slide-valve  is,  therefore,  moving  rapidly  at  that  point ; 
and  in  order  to  set  it  to  its  proper  lead  at  the  commencement 
of  the  stroke,  the  exact  dead-center  position  of  the  crank  must 
be  ascertained.  It  may  be  done  in  the  following  manner : 

Place  crank  near  dead -center,  and  make  a  mark  at  the  edge 
of  the  wheel  by  placing  a  tram,  or  stick,  against  the  floor,  or 
some  other  fixed  object  near  the  rim  of  the  wheel;  also  mark 
position  of  cross-head ;  then  turn  engine  over  dead  center  until 
cross-head  returns  to  position  first  marked ;  mark  rim  again  with 
same  tram,  in  same  manner.  Now  put  a  mark  on  rim  centrally 
between  the  two  tram-marks,  and  turn  wheel  till  this  mark  coin- 
cioles  with  tram-point.  This  is  the  exact  dead-center  position. 
Locate  the  opposite  dead  center  in  exactly  the  same  manner, 
and  set  the  valve  to  give  equal  leads.  If  there  is  lost  motion  in 
the  brasses  it  is  not  possible  to  determine  the  stroke  of  the 
piston  exactly,  but  any  material  error  in  the  valve-setting  may 
be  obviated  by  turning  the  crank  in  one  direction  only, 


THE  SLIDE-VALVE   AXD   ITS  FUNCTIONS. 


CHAPTER    II. 

IMPROVED     SLIDE-VALVES. 
THE    DOUBLE-PORTED    MARINE    SLIDE-VALVE. 

PLAIN  double-ported  slide-valves,  constructed  as  shown  in 
Fig.  14,  are  often  used  on  marine  engines.  The  valve  is  shown 
in  its  middle  position,  and  it  will  be  observed  that  the  two  con- 
jugate ports  are  exactly  alike,  and  that  they  are  opened  and 
closed  simultaneously.  Transverse  tapered  passages  in  the 
valve  admit  steam  from  the  steam-chest  to  the  inner  ports,  and 


Fig 


Double-Ported  Marine  Slide-Valve. 


a  central  duct,  cored  in  the  valve,  conveys  the  exhaust  from 
the  outer  ports,  over  the  transverse  steam-passages  to  the*  com- 
mon central  'exhaust  opening. 

In  marine  engines  the  intermediate  and  low-pressure  valves 
are  not  used  for  short  cut-off ;  but  as  the  throw  is  usually  the 
same  for  all  the  cylinders,  and  therefore  proportionately  short 
for  the  large  cylinders,  double  ports  become  desirable.  In  such 
cylinders  the  unbalanced  pressure  is  moderate,  and  unbalanced 
valves  with  short  throw  work  satisfactory. 


IMPRO  VED   SLIDE-  VA L  VES. 


85 


For  the  smaller  cylinders  —  where    smaller  valves   are   re- 
quired, and  the  throw  is  comparatively  greater,  and  where  the 
differential    pressure    occasionally    becomes    considerable,    and 
where  the  high  temperature  makes  lubrication  less  effective  — 
single-ported  piston-valves  are  generally  used. 

The  double  ports  necessarily  increase  the  clearance  and  the 
cooling  surface ;  but  in  large  cylinders,  where  steam  is  cut  off 
near  half  stroke  and  extreme  variation  in  temperature  is 
avoided,  this  becomes  of  less  consequence. 

Quite  a  number  of  special  valve-gears  are  in  use,  by  which  a 
quick  and  ample  port  opening  is  obtained  with  early  cut-off,  and 
thus  one  of  the  objections  to  single-valve  variable  cut-off  is 
removed  ;  but,  as  previously  explained,  the  evil  of  premature 
release  and  variable  compression  are  attributes  of  the  single 
valve,  and  cannot  be  amended  or  ameliorated  by  any  simple 
valve  gear. 

THE    ALLEN    LOCOMOTIVE    VALVE.* 

As  representatives  of  the  double  admission  type,  the  Allen 
locomotive-valve  and  the  Straight-Line  balanced  valve  are 
shown  in  Figs.  15  and  16. 


Fig.  15.     The  Allen  Locomotive  Valve. 

In  the  Allen  valve,  Fig.  15,  a  single,  long,  double-ported 
steam-passage,  A,  takes  steam  over  supplementary  steam  edges, 
so  located  as  to  open  and  close  the  entrance  opening  of  the  pas- 

*  This  valve  is  called  the  Trick  valve  in  Germany,  after  the  German  inventor. 


36 


THE  SLIDE-VALVE   AND   ITS  FUNCTIONS. 


sage  simultaneously  with  the  opening  and  closing  of  the  main 
port.  This  passage  never  communicates  with  the  exhaust  ;  for 
its  outlet  to  the  main  port  is  closed  just  before  the  port  opens 
for  release,  and  it  is  opened  just  after  the  port  is  closed  for  the 
exhaust,  and  it  is  then  filled  with  compressed  exhaust  steam. 
By  short  travel  the  heavy  compression  fills  it  with  dense  steam, 
and  it  ought  to  serve  its  purpose  well ;  but  when  the  travel  of 
the  valve  is  increased  under  heavy  load,  it  becomes  of  no  use, 
and  there  will  then  be  a  small  loss  by  filling  it  with  live  steam 
at  the  commencement  of  each  stroke. 

THE    STRAIGHT-LINE    BALANCED    VALVE. 

The  Straight-Line  valve,  Fig.  16,  is  the  pioneer,  and  em- 
bodies all  the  principal  features  of  the  class  of  valves  it  repre- 
sents. It  is  a  double-faced  valve,  the  two  opposite  faces  being 
exactly  alike.  It  is  confined  between  the  cylinder  valve-face 
and  an  exactly  similar  face  of  the  stationary  "  pressure-plate  "  C, 
which  plate  carries  the  unbalanced  steam  pressure  that  would 


The  Straight-Line  Valve. 


otherwise  be  carried  by  the  valve.  This  pressure  plate  is  held 
in  its  proper  position  by  distance  pieces,  which  allow  the  valve 
to  move  freely  between  the  opposite  faces.  This  construction 
provides  two  pairs  of  steam  edges  at  each  end  of  the  valve,  and 
two  port  openings  are  obtained,  as  shown  by  the  arrows.  The 
passage  A  conveys  the  steam  from  the  shallow  recess  in  the 
pressure  plate  to  the  main  port,  and  it  operates  exactly  as 


IMPROVED   SLIDE-VALVES.  37 

the  corresponding  passage  in  the  Allen  valve.  It  is  therefore 
desirable  to  restrict  this  space  as  much  as  is  possible  without 
destroying  its  usefulness.  In  case  of  the  flat  balanced  valve, 
this  presents  no  practical  difficulty  ;  but  such  narrow  passage 
could  not  easily  be  cast  in  an  Allen  valve. 

The  recesses  in  the  pressure  plate  are  not  merely  steam- 
passages,  they  are  also  there  to  equalize  the  pressure  on  both 
sides  of  the  valve.  They  may  be  considered  as  extensions  of 
the  main  steam-passages  and  as  additions  to  the  clearance 
space  ;  and  being  half  the  time  exposed  to  exhaust  steam,  the 
additional  surface  they  expose  to  the  entering  steam  is  one  of 
the  less  desirable  features  of  this  and  all  other  balanced 
valves. 

The  main  object  with  the  exhaust  passage  B  is  to  get  a 
"quick"  opening  and  closing  of  the  exhaust,  so  as  to.  avoid 
"wire-drawing."  After  the  exhaust  is  cut  off  part  of  it  is  com- 
pressed in  this  space,  and  is  bottled  up  there  before  live  steam 
enters  the  port  ;  and  directly  after  this  is  cut  off  the  bottled-up 
steam  is  allowed  to  mingle  with  the  expanding  steam  in  the 
cylinder. 

If  a  considerable  quantity  of  water  is  carried  over  in  the 
cylinder  it  may  fill  the  clearance  space,  and  force  the  valve  and 
pressure-plate  from  their  seats,  while  the  water  is  discharged  in 
the  steam-chest  ;  and  thus  the  cylinder  is  relieved  of  a  danger- 
ous strain,  while  the  clatter  of  the  valve  attracts  the  attention 
of  the  engineer. 

This  valve  is  used  in  connection  with  a  shaft  governor,  which 
automatically  changes  the  throw  and  angular  advance  of  the 
eccentric  by  shifting  it  across  the  shaft. 

An  automatic  induction  valve  of  the  Straight-Line  type  is 
sometimes  used  conjointly  with  an  exhaust  valve  of  the  same 
type  actuated  by  a  permanent  eccentric.  These  valves  are 
placed  on  opposite  sides  of  the  cylinder,  and  are  similar  in  con- 
struction to  the  combination  valve  shown  in  Fig.  16.  The 


38  THE  SLIDE-VALVE   AND   ITS  FUNCTIONS. 

main  object  with  this  arrangement  is  to  have  constant  release 
and  compression,  as  explained  in  the  first  chapter. 

The  exhaust  pressure-plate  must  be  held  to  its  seat  by 
mechanical  means  ;  and  it  may  be  done  by  springs,  in  which  case 
it  affords  a  direct  escape  for  entrapped  water  to  the  exhaust 
pipe. 

It  is  questionable  whether  a  double  exhaust  opening  is  use- 
ful, or  even  desirable,  if  the  valve  has  no  exhaust  lap  ;  for  in 
that  case,  it  opens  and  closes  for  the  exhaust  when  the  eccentric 
is  at  "half  throw,"  which  is  the  most  favorable  condition  for 
rapid  action  ;  and  as  the  exhaust  opening  for  such  valve  is  equal 
to  lap  plus  lead,  irrespective  of  the  throw,  when  the  opposite 
steam-port  opens,  or  practically  at  the  end  of  the  stroke,  the 
early  release  cannot  be  necessary ;  and  it  is  a  natural  conclusion 
that  a  slow  opening  will  be  advantageous  under  such  conditions. 
The  exhaust  closure  cannot  be  too  "  quick,"  but  it  is  a  question 
if  the  loss  by  quick  opening  is  not  greater  than  the  gain  by 
quick  closing.  With  late  admission  and  some  exhaust  lap,  two 
exhaust  openings  may  become  desirable. 

VARIATIONS    OF    THE    STRAIGHT-LINE    VALVE. 

The  valves  and  pressure-plates  of  the  Straight-Line  type  are 
sometimes  so  constructed  that  they  cannot  be  forced  from  their 
seats,  and  these  valves  admit  steam  through  a  central  opening, 
and  exhaust  it  over  the  outside  edges ;  which  leaves  exhaust 
pressure  in  the  steam-chest  and  makes  packing  of  chest  cover 
and  stem  easy,  and  it  also  allows  examination  of  the  valve  with 
steam-pressure  on.  The  transposition  of  steam-  and  exhaust- 
edges  brings  the  eccentric  in  a  diametrically  opposite  position 
on  the  shaft. 

Some  valves  of  the  Straight-Line  type  open  and  close  for 
steam  simultaneously  in  four  places,  in  which  case  two  extra 
pairs  of  steam  edges  on  opposite  valve-faces  are  disposed  much 
like  the  two  supplementary  steam  edges  of  the  Allen  valve,  and 


IMPR  O I  'ED   SL  IDE- 1  'A  L  VES. 


39 


this  necessitates  one  or  two  steam-passages  lengthwise  through 
the  valve  body.  By  reason  of  the  double  face  twice  as  many 
openings  are  obtained  as  with  the  single-faced  Allen  valve. 


THE    McEWEN    VALVE. 


A  slide-valve  is  supposed  to  be  in  perfect  equilibrium  when 
the  steam-pressure  is  equally  distributed  on  opposite  faces, 
neglecting  the  weight  of  the  valve,  which  is  generally  of  little 
consequence.  This  condition  is  presumed  to  be  satisfactorily 


J* 

Fig.  17. 


The  McEwen  Valve. 


fulfilled  when  there  are  channels  or  recesses,  back  of  the  valve, 
in  form  and  area  equal  to,  and  exactly  opposite  the  ports  and 
the  exhaust  area  in  front  of  the  valve,  and  means  provided  for 
continuous  communication  between  opposite  sides.  It  must, 
however,  be  admitted  that,  under  the  conditions  which  generally 


40 


THE   SLIDE-VALVE   AND   ITS  FUNCTIONS. 


prevail,  the  intensity  of  the  pressure  on  both  sides- of  a  balanced 
valve  cannot  be  absolutely  uniform  ;  for  when  the  ports  are 
only  partly  covered  by  the  valve,  and  steam  is  rushing  through 
the  ports  with  a  velocity  of  one  hundred  feet,  or  more,  per 
second,  there  is  practically  no  pressure  on  that  surface  which 
overlaps  the  port  edge,  while  the  pressure  on  the  corresponding 
opposite  surface,  on  the  back  of  the  valve,  must  of  necessity  be 
considerably  greater,  partly  on  account  of  the  dynamic  effect 
of  the  steam,  and  partly  from  the  resistance  the  flow  of  steam 
encounters  in  the  passages  back  of  the  valve. 

This  undesirable  feature  is  avoided   in   the  design  of   the 
McEwen  valve,  shown  in  section    in   Fig.    17.     The   valve    is 

of  flat,  rectangular 
form,  and  is  of  the 
"Straight-Line"  type; 
but,  unlike  Professor 
Sweet's  valve,  it  has 
no  auxiliary  passage 
through  the  valve. 
The  valve  is  covered 
by  a  pressure-plate,  in 
which  are  auxiliary 
steam-passages,  the 
ports  of  which  are 


o       o       o       o      o       o 

0 

(S 

„ 

1 

x  v 

J 

: 

3 

o 

o 

o 

-^^— 

0 

(c 

~ 

r 

"VST 

1 

4 

b 

0 

_ 

o       o       o       o       o       o 

Fig.  18. 


opposite  to  the  ports  in  front  of  the  valve,  and  being  simul- 
taneously uncovered  by  the  valve,  these  ports  permit  the  steam 
to  flow  in  opposite  directions  from  opposite  valve-faces,  thus 
leaving  the  valve  in  perfect  equilibrium. 

The  valve-face  on  the  cylinder  is  shown  in  Fig.  18,  and  it 
will  be  understood  that  the  pressure  plate  has  four  hollow  legs, 
by  which  steam  is  conducted  through  the  four  smaller  ports 
into  the  main  steam-passages  to  the  cylinder  ;  and  the  exhaust 
will  escape  through  the  same  ports. 


IMPROVED   SLIDE-VALVES, 


THE    BALL    TELESCOPIC    VALVE. 


41 


//  The  excessive  unbalanced  pressure  on  the  common  D-valve, 
which  causes  friction  and  rapid  wear,  is  mainly  due  to  the  large 
exhaust  cavity  which  permanently  removes  steam-pressure  from 
a  large  area  on  the  face-side  of  the  valve,  while  the  entire  rear 
side  is  exposed  to  full  steam-pressure.  By  admitting  steam 
through  a  central  opening  in  the  valve,  and  exhausting  it  over 
the  outside  edges,  the  exhaust  cavity  is  dispensed  with,  and  the 
unbalanced  pressure  is  thereby  greatly  reduced. 

A  valve  designed  on  this  principle  by  Mr.  Frank  H.  Ball  is 
represented  in  Fig.    19,  which    shows  the  valve  in  its  central 


Fig.  19.     The  Ball  Telescopic  Valve. 


position  in  the  steam-chest.  It  is  a  double-faced  valve,  and  it 
consists  of  two  telescopically  connected  parts.  Each  part  con- 
sists of  a  flat  rectangular  frame,  which  covers  the  ports  in  its 
central  position,  and  on  which  is  a  short  hollow  cylinder.  One 
of  these  cylinders  fits  inside  the  other,  and  it  has  three  grooves 
containing  packing-rings.  As  these  rings  do  not  wear  at  all 
they  remain  steam  tight  when  properly  fitted.  Steam  is 
admitted  to  the  inside  of  the  valve,  as  shown,  and  the  exhaust 


42  THE   SLIDE-VALVE   AND   ITS  FUNCTIONS. 

escapes  over  the  outside  edges  into  the  steam-chest.  The  only 
unbalanced  area  is  that  portion  of  the  steam-ports  which  is 
opposite  the  cylindrical  part  of  the  valve  during  the  exhaust 
period  ;  and  taking  the  counter  pressure  into  account,  the  valve 
is  so  proportioned  as  to  leave  sufficient  unbalanced  pressure  to 
insure  a  close  contact  between  the  working  faces.  This  valve 
has  the  undoubted  advantage  that  it  will  follow  up  its  own 
wear  ;  and  the  claim  made  for  it,  that  it  remains  steam  tight 
throughout  its  entire  life,  does  not  seem  unreasonable  ;  and, 
moreover,  this  claim  is  backed  by  seventeen  years'  experience. 

The  double-port  opening  is  particularly  useful  when  the 
steam  is  cut  off  early  by  reduced  valve  travel  ;  but  it  will  be 
noticed  that  the  valve-faces  are  horizontal,  or  parallel  with 
the  top  and  bottom  of  the  steam-chest,  which  necessitates  a 
divided  and  somewhat  distorted  steam-passage  to  the  cylinder, 
and  is  a  feature  which  some  designers  studiously  avoid.  ^ 

BALANCING    A    COMMON    D-VALVE. 

The  extreme  changes  of  temperature  in  cylinder  castings 
may  warp  the  valve-faces  ;  and  for  this  and  other  reasons  a  plain 
slide-valve,  provided  with  a  self-adjusting  pressure-relieving  de- 
vice on  its  back,  is  often  used.  As  the  surfaces  are  self-adjust- 
ing extraordinary  nice  fitting  is  not  essential,  and  if  there  i's  a 
leakage  it  is  apt  to  diminish  by  wear ;  and  if  much  water  gets 
into  the  cylinder  it  may  escape  to  the  steam-chest  by  pushing 
the  valve  back  from  its  seat.  Such  a  valve  cannot  be  perfectly 
balanced ;  for  the  counter-pressure  on  the  face  depends  to  some 
extent  on .  the  position  of  the  valve,  and  is,  therefore,  not  quite 
uniform. 

Fig.  20  shows  a  plain  slide-valve  with  a  pressure-relieving 
device  suitable  for  a  horizontal  low-pressure  cylinder.  It  con- 
sists of  a  ring,  cast  on  the  back  of  the  valve,  and  a  loose  flanged 
ring,  fitted  inside  it.  The  ring  bears  against  the  steam-chest 
cover  and  keeps  steam  away  from  the  back  of  the  valve. 


IMPR O  VED   SLIDE-  VAL  VES. 


43 


The  space  inside  the  ring  must  communicate  with  the  exhaust, 
and  in  the  case  here  illustrated  the  circular  opening  extends 
through  the  back  of  the  valve  to  the  exhaust  cavity.  Small 
helical  springs  are  placed  so  as  to  keep  the  ring  out  when  the 
engine  is  started. 

The  valve  here  shown  was  designed  for  the  low-pressure 
cylinder  of  a  non-condensing  engine  and  for  a  fixed  cut-off 
at  three-eighths  of  the  stroke.  To  prevent  the  compression 
from  forcing  the  valve  out  against  low  receiver-pressure  the 
ports  were  reduced  to  about  half  their  usual  size,  as  shown  ; 
and,  as  mentioned  in  chapter  i,  this  had  no  appreciable  effect 
on  the  exhaust.  The  relieved  area 
is  that  inclosed  by  the  outside  cir- 
cumference of  the  inside  ring  or  the 
inside  circumference  of  the  outside 
ring,  and  for  a  non-condensing  engine 
it  should  not  exceed  three-quarters  of 
the  area  between  exhaust  edges.  For 
condensing  engines  it  could  and  ought 
to  be  nearly  equal  to  this  whole  area ; 
but  as  all  engines  may  incidentally  run 
non-condensing,  it  is  probably  advis- 
able to  provide  for  such  occurrence. 

On  high-pressure  cylinders  the  ring 
area  is  often  made  equal  to  the  area 
between  exhaust-edges  plus  the  area  of 
one  port. 


Fig.  20.    Plain  Valve, 
Partly  Balanced. 


The  pressure  that  keeps  the  ring  against  the  steam  chest 
cover  is  determined  by  the  difference  in  pressure  on  both  sides 
of  the  flange  A.  Professor  S.  W.  Robinson  has  shown  experi- 
mentally that  a  sliding  surface  which  separates  exhaust  from 
"live  steam  "  is  exposed  to  pressure  of  "  creeping  "  steam,  which 
decreases  nearly  uniformly  from  the  steam  side  to  the  exhaust 
side  ;  and  it  may  reasonably  be  assumed  that,  when  one  surface 


44  THE   SLIDE-VALVE   AND   ITS  FUNCTIONS. 

is  sliding  over  another  surface  which  is  alternately  exposed  to 
steam-  and  exhaust-pressure  or  high-  and  low-pressure  steam,  the 
mean  pressure  between  the  surfaces  will  be  a  mean  between 
the  extremes  on  either  side ;  but  it  may  also  reasonably  be  ex- 
pected that,  by  the  reciprocating  motion,  the  intervening  pres- 
sure becomes  somewhat  uneven  at  the  two  extremities  of  the 
travel ;  for  at  one  end  the  covered  surface  is  never  fully  exposed 
to  the  lower  pressure,  and  at  the  other  end  it  is  never  exposed 
to  the  higher  pressure,  and  in  the  extreme  positions  the  interven- 
ing pressure  may,  therefore,  alternately  approach  the  higher  and 
lower  pressure  at  diametrically  opposite  points  of  the  ring. 
On  one  face  of  the  flange  is  full  receiver-pressure,  and  on 
the  other  face  is  the  variable  intervening  pressure ;  and  it  will 
readily  be  understood  why  it  has  been  found  necessary,  in  order 
to  insure  permanent  contact,  to  make  both  flange  areas  equal 
by  turning  down  a  shallow  recess,  as  shown.  The  flange  A  can 
be  from  three-quarters  to  one  inch  wide,  and  the  springs  should 
be  very  light.  Similar  devices  are  often  used  on  locomotives. 

V j+         THE    RICHARDSON    BALANCED    VALVE. 

The  Richardson  balancing  device,  much  used  on  locomotives, 
consists  of  straight  metal  strips,  which  fit  steam-tight  in  grooves 
on  the  back  of  the  valve,  and  are  held  against  the  steam-chest 
cover  by  steam-pressure  and  springs.  These  strips  inclose  a 
rectangular  area  which  communicates  with  the  exhaust  cavity 
through  a  small  opening  in  the  back  of  the  valve. 

THE    THOMAS    BALANCE. 

Fig.  21  represents  a  balancing  device  invented  by  Mr.  W.  J. 
Thomas  and  much  used  on  locomotives.  The  ring  A  is  open  in 
one  place  and  is  expanded  some  by  being  forced  on  its  conical 
seat ;  it  is  therefore  self-adjusting,  both  against  the  conical  sur- 
face and  against  the  planed  surface  of  the  steam-chest  cover, 
and  the  steam-pressure  on  the  circumference  of  the  ring  insures 


I  If  PR  O I  'ED   SLIDE-  VA  L  VES. 


45 


a  tight  joint  between  the  ring  and  the  cone.  By  using  the 
proper  taper,  the  resultant  pressure  against  the  steam-chest  cover 
is  made  sufficient  to  overbalance  the  counter-pressure  of  creep- 
ing steam  between  the  ring  and  the  cover.  The  differential 
pressure  on  the  valve-face  is  determined  by  the  relative  propor- 
tion of  the  relieved  area.  In  locomotives  due  allowance  must 
be  made  for  removal  of  the  valve-yoke,  and,  therefore,  a  remov- 
able disk  is  used,  as  shown  in  the  cut.  If  the  steam-chest  is 
narrow,  two  rings  may  be  placed  side  by  side  on  cones  cast  on 
the  valve. 

The  manufacturers  have  established  the  following  rule  :  Bal- 
ance-ring areas  are  made  equal  to  "area  of  one  steam-port,  two 


Fig.  21.     The  Thomas  Balance. 


bridges  and  the  exhaust-port  plus  8  per  cent  if  for  single  bal- 
ance, and  plus  15  per  cent  if  for  double  balance. 'X  It  may  ap- 
pear as  if  more  pressure  is  removed  from  the  back  of  the  valve 
than  would  ordinarily  be  considered  safe,  but  the  apparent 
anomaly  disappears  when  it  is  considered  that  the  reaction  from 
the  bevel  ring-surface  must  be  balanced  ;  and  the  friction  of  the 
conical  joint,  no  doubt,  serves  a  good  purpose  by  opposing  the 
counter-pressure  of  the  exhaust-steam  when  the  link  is  at  mid- 
gear.  The  opening,  cut  in  the  ring  in  order  to  expand  it,  is  cov- 
ered by  an  L-shaped  joint-plate,  which  fits  against  the  cone  and 
is  flush  with  the  top  of  the  ring,  and  forms  a  steam-tight  joint  in 
both  places.  The  rings  are  made  of  hard,  close-grained  cast  iron ; 


46 


THE   SLIDE-VALVE   AXD   ITS  FUNCTIONS. 


and  the  outer  rim,  shown  in  the  sketch,  is  there  to  prevent  acci- 
dent if  the  ring  should  break.  As  the  ring  is  held  firmly  against 
the  cone,  there  is  no  wear  on  this  ;  and  the  ring,  being  self-adjust- 
ing, is  admirably  adapted  for  the  interchangeable  system  preva- 
lent in  locomotive  works.  This  device  may  readily  be  fitted  to 
any  common  slide-valve  or  double-admission  valve. 

That  more  balance  area  is  required  with  double  rings  is  evi- 
dently due  to  the  fact  that  the  circumference  of  two  rings  com- 
bined is  more  than  that  of  one  ring  inclosing  the  same  area,  and 
the  push  against  the  valve-seat  from  the  conical  ring  surfaces 
becomes  correspondingly  greater. 

PISTON-VALVES. 

^  Piston-valves  are  cylindrical  valves  moving  in  the  direction  of 
their  axis.  Usually  steam  is  admitted  centrally,  and  the  steam- 
ports  open  into  annular  spaces  surrounding  the  valve,  by  which 
a  perfect  balance  is  obtained.  They  are  simply  balanced  slide- 


Fig.  22.    Double-Admission  Piston-Valve. 

valves  of  convenient  form,  and  are  designed  for  single  or  double 
admission  on  the  same  principle  as  the  flat  valve.  Fig.  22  shows 
a  double-admission  piston-valve  in  its  central  position,  with  steam- 
laps  on  the  inside  between  the  ports.  The  passage  A,  in  con- 
junction with  the  narrow  annular  ports,  provides  for  double  ad- 


IMPR 0  VED   SLIDE-  VAL  VES. 


mission,  as  does  the  corresponding  passage  of  the  Allen  valve ; 
and  like  this  it  should  be  so  placed  that  it  never  communicates 
with  the  exhaust,  in  order  to  save  the  residual  steam  it  contains 
and  to  avoid  condensation.  The  admission-edge  and  the  exhaust 
edge  of  a  piston-valve  extend  all  around  its  circumference,  and 
for  this  reason  a  comparatively  small  diameter  will  give  sufficient 
port-opening.  Double-admission  piston-valves  are  seldom  pro- 
vided with  adjustable  packing-rings,  while  it  is  common  on  single- 
admission  valves.  All  piston-valves  work  in  removable  bush- 
ings, in  which  the  ports  are  cut  out.  Judging  from  recent  prac- 
tice the  double-admission  piston-valve  may  become  obsolete.  ^ 

VALVES    OF    THE    "IDEAL    ENGINE." 

//- Piston-valves  of  the  "Ideal  Engine"  are  shown  in  Figs.  23 
and  24.  One  is  a  plain  valve  without  rings,  and  the  other  is  an 
"expansive  "  valve.  Only  one  end  of  the  latter  is  shown,  and  the 
scale  is  sufficiently  large  to  show  details  of  construction  plainly. 
The  two  rings,  A,  are  made  to  fit  the  bore  accurately,  and 


I 


Fig.  23.     "Ideal"  Valve. 


are  then  split  to  allow  of  some  expansion.  They  are  not  "  spring- 
rings,'  '  for  they  ape  thick  and  not  made  larger  than  the  valve-bore 
of  the  cylinder./ When  the  valve  becomes  leaky  from  wear  the 
rings  may  be  expanded  a  little  by  turning  the  head  B.  This  head 


48 


THE  SLIDE-VALVE   AND   ITS  FUNCTIONS. 


has  a  ring-formed  extension,  on  which  are  four  cams  or  eccentric 
planes.  These  are  accurately  machined,  and  bear  on  four  shoes 
C,  which  fit  against  the  inside  periphery  of  the  expansion  rings. 
Thus  by  turning  the  head  the  four  shoes  are  simultaneously 
forced  against  the  rings,  and  by  thus  expanding  them,  a  delicate 
adjustment  to  the  proper  diameter  is  made.  After  adjustment 
is  made,  the  nut  D  is  screwed  up  tight,  clamping  the  head  and 


Fig.  24.    The  "Ideal"  Expansive- Valve. 

rings  securely.  The  object  is  evidently  to  avoid  the  use  of  spring 
rings,  which  would  wear  the  valve-seat,  and  would  have^po  be 
very  thin  on  small  valves,  and  would  be  liable  to  break.  '* 

The  builders  of  the  Ideal  Engine  also  use  flat-balanced  valves 
of  the  Straight- Line  type ;  and  in  view  of  the  fact  that  there  has 
at  times  been  a  lively  controversy  about  the  relative  merits  of 
these  two  valve  types,  the  following  letter  from  the  Ideal  En- 
gine builders  is  interesting : 

DEAR  SIR,  —  In  reply  to  your  letter  of  the  2d  inst.  Although  \ve  offer 
purchasers  the  option  of  taking  the  plain  solid  valve  or  our  patented  adjustable 
valve,  three-fourths  of  our  sales  are  for  the  plain  solid  valve.  The  valve-seats  or 


IMPROVED   SLIDE-VALVES.  49 

bushings,  after  being  pressed  into  the  'steam-chest  chambers,  are  bored  out  with 
a  portable  bar,  and  then  a  reamer  put  through,  and  a  valve  is  fitted  which  has 
been  previously  ground  on  a  Brown  &  Sharpe  grinding  machine  for  an  accurate 
and  close  fit.  By  this  method  we  get  a  valve  that  is  perfectly  balanced,  and  is 
practically  steam  tight,  and  requires  less  lubrication  than  valves  of  the  flat  type, 
and,  consequently,  gives  excellent  service.  ^  Three  to  five  years'  service  can  be  had 
before  the  valve  is  worn  sufficient  to  cause  excessive  loss  of  steam  and  require 
renewal ;  and  then  renewal  is  so  easily  and  cheaply  made  by  means  again  of  the 
portable  boring  rig.  The  valves  are  light  and  give  satisfaction  in  everybody's 
hands.  The  adjustable  valve  is  all  right,  but  in  hands  of  careless  or  incompetent 
engineers  it  can  be  expanded  so  tight  as  to  cause  stripping  of  the  valve  gear. 

We  are  also  builders  of  flat  balanced  valves,  but  our  greatest  sales  are  the 
piston  valve;  and  after  having  had  experience  with  both   types  we  believe  the 
piston  valve  to  be  the  best  commercial  design. 
JAN.  6,  1902. 

THE    WESTINGHOUSE    STANDARD    VALVE. 

^X'  Fig.  25  (on  the  following  page)  represents  a  sectional  view  of 
cylinders  and  valve  of  a  Westinghouse  Standard  Engine.  This 
is  a  two-cylinder  vertical  engine,  and  the  cylinders  take  steam 
on  the  down-stroke  only.  Admission  and  exhaust  are  controlled 
by  a  single  piston-valve,  located  between  the  cylinders.  The 
pistons  move  in  opposite  directions ;  and  the  cut  shows  the 
left-hand  piston  (in  sections)  at  its  highest  position,  and  the  valve 
just  commencing  to  uncover  the  steam-port ;  while  the  port 
on  the  other  side  is  already  uncovered  sufficiently  for  a  free 
exhaust.^  The  live  steam  is  confined  in  the  annular  space,  sur- 
rounding the  valve,  and  the  hollow  valve  body  and  the  upper 
and  lower  parts  of  the  valve-chamber  receive  the  exhaust  steam. 
It  will  be  seen  that  the  valve  arrangement  is  practically  the 
same  as  that  of  a  single-cylinder  double-acting  engine  ;  the  only 
difference  is^  that  in  the  case  under  review,  the  steam-ports  are 
on  opposite  sides  of  the  valve. 

The  small  piston  above  the  valve  is  there  to  balance  the 
reciprocating  force  of  the  valve  and  its  connections,  that  is,  to 
overcome  the  momentum  of  these  parts.  The  exhaust  steam 
and  air  confined  in  the  upper  part  of  the  steam-chest  above  the 


50  THE   SLIDE-VALVE   AXD   ITS  FUNCTIONS. 

piston,  is  alternately  compressed  and  expanded,  and  offers  an 
elastic  resistance,  similar  to  that  of  a  spring,  alternately  com- 
pressed and  extended ;  and  this  elastic  force  is  directly  opposed 
to  and  partly  neutralizes  the  reciprocating  force  of  the  valve. 


Fig.  25.     The  Westinghouse  Standard. 

The  valve  is  driven  by  means  of  a  sh  if  table  eccentric  con- 
trolled by  a  shaft  governor,  and  the  point  of  cut-off  is  automati- 
cally varied  by  changing  the  throw  and  angular  advance  of  the 
eccentric ;  that  is,  by  moving  it  across  the  shaft  in  a  suitable 
manner. 

VALVES    ON    COMPOUND    ENGINES. 

The  valves  of  tandem-compound  engines  are  frequently 
driven  by  a  single  shifting  eccentric,  which  automatically  changes 
the  cut-off  in  both  cylinders.  In  such  case  the  high-  and  low- 
pressure  cut-off  must  nearly  coincide ;  for,  the  angular  advance 


JMTRO  J  'ED   SLIDE-  VAL  J  '£S. 


51 


being  the  same  for  both  valves,  the  cut-off  can  only  be  made 
different  by  varying  the  laps ;  and  as  this  changes  the  lead  it  is 
only  permissible  within  narrow  limits.  Such  arrangement  is 
probably  favorable  to  close  regulation,  and  it  has  the  advantage 
of  great  simplicity ;  but  whether  it  has  any  economical  advan- 
tage or  disadvantage  has  not  been  practically  demonstrated.  If 
both  valves  have  the  same  travel,  the  port-opening  to  the  low- 
pressure  cylinder  will  be  very  small  comparatively,  even  if  the 
length  of  the  port  is  proportioned  to  the  cylinder-bore ;  and 
on  account  of  the  high  receiver  pressure  by  early  cut-off,  a 
"nice"  Hirgh-pressure  "card"  cannot  be  expected  when  the 
engine  is  under-loaded. 

Some  compound  engines  have  a  single  piston-valve,  driven 
by  a  shifting  eccentric  .or  a  link-gear.  The  cylinders  are 
arran'ged  side  by  side,  with  the  valve  in  an  intermediate  or 
parallel  position,  and  both  cylin- 
ders and  valve-chamber  are  made 
in  one  casting ;  and  in  this  com- 
bination the  piston-valve  has  prob- 
ably reached  the  acme  of  fitness 
and  simplicity.  Fig.  26  may  rep- 
resent a  valve  of  this  type  for  a 
small  vertio&i  compound-engine 
having  two  cranks  oppositely  dis-- 
posed.  The  central  part  of  the 
valve  bushing  is.  surrounded  by 
steam,  which  is  admitted  through 
an  annular  port  to  the  annular 
valve-space,  which  connects  with 


Fig.  26.    Compound  Piston- Valve. 


the  high -pressure  cylinder,  as  shown.  The  valve  has  just 
opened 'for  steam  to  the  upper  end  of  the  high-pressure  cylin- 
der-, and  the  exhaust  from  the  lower  end  is  just  entering  the 
low-pressure  cylinder,  while  the  low-pressure  exhaust  is  escap- 
ing from  the  upper  end  through  the  hollow  valve  to  the  lower 


52  THE   SLIDE-VALVE   AND   ITS  FUXCTIOXS. 

exhaust-chamber.  The  steam-distribution  is  regulated  by  three 
ports  :  The  central  port  admits  and  cuts  off  steam  to  the  high- 
pressure  cylinder,  while  the  two  other  ports  control  the  admis- 
sion of  high-pressure  exhaust  to  the  low-pressure  cylinder,  and 
also  the  exhaust  from  this  cylinder.  The  exit  from  the  high- 
pressure  cylinder  is  not  directly  controlled  by  the  valve  ;  the 
expanded  steam  simply  gets  out  as  soon  as  it  has  a  chance  to 
go  into  the  low-pressure  cylinder. 

Release  and  exhaust  closure  in  the  high-pressure  cylinder 
become  coincident  with  admission  and  cut-off  in  the  low-pressure 
cylinder.  The  admission  lap  for  the  low-pressure  side  becomes 
the  exhaust  lap  for  the  high-pressure  side.  This  feature  is  open 
to  criticism ;  for  some  lap  is  required  to  avoid  excessive  lead  to 
the  low-pressure  cylinder,  while  for  the  high-pressure  exhaust 
no  lap  or  negative  lap  is  preferable,  for  the  compression  of  the 
intermediate  exhaust  may  otherwise  become  excessive.  Experi- 
ence has  established  the  fact  that  smooth  running  is  hardly 
obtainable  with  excessive  compression,  but  as  to  steam  economy 
the  only  satisfactory  answer  can  be  furnished  by  a  strictly  sci- 
entific comparative  test. 

Considering  that  space  which  is  always  in  direct  communi- 
cation with  the  cylinder  is  "clearance-space,"  it  appears  that 
there  is  no  "receiver-space,"  for  the  low-pressure  cylinder  takes 
steam  directly  from  the  high-pressure  clearance-space.  This 
space  is  extraordinarily  large,  and  when  steam  and  exhaust  are 
cut  off  late  in  the  stroke  it  may  cost  something  to  fill  it  with 
steam  at  the  commencement  of  each  stroke  ;  though  under  cer- 
tain conditions  this  loss  may  be  very  insignificant,  considering 
that  this  space  never  communicates  with  the  atmosphere  or  the 
condenser ;  and  it  is  probably  very  useful  as  a  means  of  keeping 
down  the  compression  in  the  high-pressure  cylinder.  These 
valves  are  usually  fitted  with  packing-rings. 


IMPROVED   SLIDE- VAL VES. 


THE    WESTINGHOUSE    COMPOUND    VALVE. 

Fig.  27  shows  the  valve  of  a  Westinghouse  Compound 
Engine  which  is  vertical  and  single-acting.  The  valve  is  of 
the  piston  type,  hollow  and  light,  and  made  steam-tight  by 
means  of  four  spring  rings.  It  is  operated  by  means  of  a 
bell-crank  rocker  from  a  shiftable  eccentric,  controlled  by  a 
shaft  governor.  The 
steam-passages  are 
formed  by  a  hard  cast- 
iron  bushing,  forced 
into  place.  By  this  con- 
struction the  ports  can 
be  machined  to  exact 
size  and  register.  S 
and  E  are  the  steam 
and  exhaust  chambers 
around  the  bushing, 
into  which  connects  re- 
spectively the  steam  Fig'  *7'  ,The  Westinghouse  Compound, 
and  exhaust  pipe.  The  valve  is  shown  in  its  central  position 
covering  the  high-  and  low-pressure  ports.  The  ports  consist 
of  annular  series  of  openings  surrounding  the  valve.  The  high- 
pressure  port  is  seen  to  the  left,  centrally  over  the  high- pressure 
cylinder.  Next  to  this  is  an  open  passage  from  the  high- 
pressure  cylinder  to  the  space  surrounding  the  neck  of  the 
valve.  B  is  a  by-pass  valve,  used  only  for  starting  the  engine. 
Next  to  this  is  the  low-pressure  port,  also  covered  by  the  valve. 

The  high-pressure  port  is  only  for  admission  to  the  high- 
pressure  cylinder,  while  the  low-pressure  port  is  for  admission 
and  exhaust  to  and  from  the  low-pressure  cylinder,  and  it  also 
controls  the  exhaust  from  the  high -pressure  cylinder.  The 
space  around  the  neck  of  the  valve  is  part  of  the  clearance 
space  of  the  high-pressure  cylinder ;  the  pressure  in  this  space 


54  THE   SLIDE-VALVE   AND   ITS  FUXCT1OXS. 

is  always  the  same  as  that  in  the  adjoining  cylinder,  being- 
always  in  direct  communication  with  it.  It  is  never  in  direct 
communication  with  the  low-pressure  exhaust. 

The  large  high-pressure  clearance  has  been  criticised  from  a 
theoretical  standpoint,  without  regard  to  the  fact  that  it  cannot 
consistently  be  considered  equivalent  to,  or  compared  with,  the 
clearance  of  the  low-pressure  cylinder  or  that  of  a  simple  en- 
gine. This  is  what  the  Westinghouse  people  have  to  say  to 
their  critics :  "  We  have  no  quarrel  with  theory,  but  only  with 
mistaken  interpretation  of  theory,  and  we  simply  submit  that 
the  practical  results  obtained  from  this  design  should  set  at 
naught  the  unsupported  opinion  of  those  who  decry  the  method 
employed." 

The  pistons  are  of  the  trunk  pattern,  and  it  will  be  observed 
that  the  low-pressure  piston  has  two  diameters.  The  lower  part 
works  through  an  internal  sleeve,  or  cylinder,  which  connects 
with  the  crank-case.  By  this  construction  the  piston  displace- 
ments in  relation  to  the  crank-case  become  equal,  and  suction 
and  expulsion  of  air  and  oil  through  the  vent-pipe  in  the  crank- 
case  is  avoided.  The  air  confined  in  the  annular  space  under- 
neath the  large  diameter,  being  alternately  compressed  and 
expanded,  helps  to  overcome  the  inertia  of  the  large  piston. 

THE    VAUCLAIN    VALVE.     ' 

The  Vauclain  Compound  Locomotive  has  one  high-pressure 
cylinder  and  one  low-pressure  cylinder  on  each  side,  and  their 
volumetric  ratio  is  about  as  one  to  three.  They  are  cast  in  one 
piece  with  the  valve  chamber  and  saddle,  the  cylinders  being  in 
the  same  vertical  plane,  and  close  together.  Fig.  28  shows 
the  arrangement  for  "  eight-wheel "  passenger  locomotives. 
The  valve  is  located  in  the  saddle  of  the  cylinders  casting,  be- 
tween the  cylinders  and  the  smoke-box.  The  steam-chest  is 
bored  out,  and  a  bushing  with  accurately  machined  ports  is 
forced  in.  The  valve,  shown  in  half-section  in  Fig.  29,  is  of 


IMPROVED  SLIDE-VALVES.  55 

the  piston  type  —  double  and  hollow  —  and  it  controls  the 
admission  and  exhaust  of  both  cylinders.  The  pistons  — 
secured  to  a  common  cross-head  —  move  in  unison  ;  and  the  ex- 
haust steam  from  the  high-pressure  cylinder,  becoming  the 
supply  steam  for  the  low-pressure  cylinder,  is  conveyed  from 
the  high-pressure  port  through  the  hollow  valve  to  the  low- 
pressure  port  at  the  opposite  end.  The  operation  of  the  valve 
can  be  readily  understood  by  considering  it  as  two  valves  com- 
bined —  one  for  the  high-pressure  cylinder  ports,  and  a  shorter 
one  for  the  low-pressure 
ports.  The  valve  is 
shown  in  its  central  po- 
sition ;  and  it  will  -be 
seen  that  the  laps  are 
equal,  and  that  steam  is 
admitted  over  outside 
port  edges  and  expelled 
over  inside  port  edges. 
Live  steam  is  conducted 
to  both  ends  of  the  valve- 
chamber,  and  is  finally 
exhausted  in  the  central 
cavity,  which  connects 
with  the  exhaust-pipe.  FiS-  28- 

There  is  negative  lap  on  the  exhaust  side,  and  the  steam  will 
be  released  in  the  high-pressure  cylinder  before  it  is  admitted  to 
the  low-pressure  cylinder.  In  the  meantime  it  is  stored  in  the 
hollow  valve-body,  which  thus  serves  as  a  receiver,  and  makes  it 
practicable  to  use  admission  lap  for  the  low-pressure  cylinder. 

In  locomotives  it  is  necessary  to  restrict  the  exhaust  outlet 
in  order  to  get  the  benefit  of  expansion  in  the  smoke-box,  and 
the  back-pressure  tends  to  increase  the  compression  in  the  low- 
pressure  cylinder  ;  an  early  exhaust  closure  is,  therefore,  not 
desirable,  and  it  is  avoided  by  means  of  a  negative  exhaust  lap. 


56 


THE  SLIDE-VALVE   AND   ITS  FUNCTIONS. 


LOW-PRESSURE:  CYLINDER 

Fig.  29.     The  Vauclain  Valve. 

On  the  high-pressure  side  the  exhaust  lap  is  also  negative,  for 
otherwise  the  density  of  the  receiver-steam  would  bring  the 
compression  up  too  high.  It  is  not  necessary  to  cut  off  earlier 

than  half-stroke,  for  this  gives  six 
nominal  expansions ;  and  thus  a  larger 
port-opening  and  more  decisive  cut- 
off action  is  incidentally  gained  by 
compounding. 

A  reduced  indicator  diagram  is 
shown  in  Fig.  30.  The  point  of  re- 
lease is  easily  discernible  in  the  high- 
pressure  diagram,  and  it  will  be 
noticed  that  the  expansion  is  checked  before  the  low-pressure 
port  is  open.  This  is  not  remarkable,  considering  the  small 
capacity  of  the  receiver. 


I.H.P.    1370 

Fig.  30. 


IMPKO  VED   SLIDE-  VAL  VES. 


57 


THE  ALLFKEE  VALVE— GEAR. 

There  are  several  well-founded  objections  to  the  use  of  a 
single  valve  in  variable  cut-off  engines  and  locomotives.  The 
small  port-opening,  the  slow  cut-off  action,  the  early  release,  and 
the  extremely  variable  compression  are  not  desirable  features. 
There  are  various  valve-gears  in  use,  which  give  ample  port- 
opening,  but  they  -do  not  correct  the  premature  release  and 
early  exhaust  closure.  The  ordinary  valve-motion,  when  cutting 
off  at  half-stroke,  is  represented  in  diagram  31.  As  explained 
in  chapter  i,  the  two  lap  lines  must 
be  parallel ;  and  arcs  4-6  and  1-9 
must,  therefore,  necessarily  represent 
equal  intervals  of  time,  that  is,  the 
interval  between  cut-off  and  release, 
and  between  exhaust  closure  and  ad- 
mission, must,  under  all  conditions, 
be  equal.  When  the  valve  cuts  off 
at  half-stroke,  the  release  and  com- 
pression may  be  quite  satisfactory  ; 
but  at  earlier  cut-off,  when  the  full 
benefit  of  expansion  is  obtained,  the 
exhaust  action  becomes  less  satisfac- 
tory. The  compression  may  not  be- 


Fig.  31- 


come  excessive  if  there  is  considerable  clearance ;  but  the  vari- 
ableness of  the  compression  is  unavoidable ;  and  it  may  safely 
be  assumed  that  much  clearance  is  not  conducive  to  steam 
economy. 

If  the  exhaust-cord  would  remain  as  shown  in  Fig.  31,  a 
small  clearance  would  suffice,  and  the  release  would  be  satisfac- 
tory. Practically,  these  are  the  conditions  existing  in  the  All- 
free  single-valve  engine.  The  valve-gear  is  shown  in  Fig.  32. 
There  are  a  toothed  sector,  a  pinion,  and  a  small  eccentric 
mounted  in  the  rocker-arm.  While  the  rocker-arm  is  actuated 


58 


THE   SLIDE-VALVE   AND   ITS  FU AUCTIONS. 


in  the  ordinary  manner  from 
the  governing  eccentric,  the 
sector  is  operated  from  a  fixed 
eccentric  keyed  upon  the  shaft. 
By  this  means  a  rotary  motion 
is  imparted  to  the  pinion-shaft. 
This  shaft  is  made  from  a  solid 
piece  of  machinery  steel,  having 
an  eccentric  of  about  ;  '  radius 

o 

formed  at  one  end.  This  eccen- 
tric is  connected  through  a  small 
link  to  the  valve-stem.  In  oper- 
ation, if  the  rocker  arm  is  allowed 
to  stand  fixed,  and  the  engine 
rolled  over,  the  eccentric  on  the 
pinion-shaft  would  move  the 
valve  three-fourths  of  an  inch. 
If  the  rocker  arm  is  allowed  to 
operate,  the  small  eccentric  will 
make  nearly  a  whole  turn  while 
the  rocker  moves  from  one  ex- 
tremity of  its  throw  to  the  other ; 
and  it  will  be  clear  that,  during 
the  rotation  of  the  eccentric,  and 
the  movement  of  the  rocker  arm, 
at  certain  predetermined  points 
the  two  movements  will  coincide 
and  others  will  oppose.  It  gives 
the  valve  a  high  speed  at  the 
time  of  opening  and  closing,  and 
a  slow  speed  or  pause  during  ex- 
pansion. Thus  the  valve  is 
caused  to  open  for  a  given  cut- 
off about  twice  as  wide  as  in  an 


IMPROVED  SLIDE-VALVES.  59 

ordinary  automatic.  The  advantage  thus  secured  for  the  steam 
admission  is  likewise  secured  for  the  exhaust. 

In  Fig.  33  let  the  main  eccentric  be  held  by  the  governor  in 
position  B  for  latest  cut-off,  and  let  E  mark  the  position  of  the 
fixed  eccentric,  then  angle  V  represents  the  angular  advance 
of  the  main  eccentric  in  relation  to  the  fixed  eccentric.  When 
the  main  eccentric  has  been  moved  to  position  B'  for  shortest 
cut-off  the  angle  between  the  eccentrics  has  been  increased 
to  1 80°.  The  throw  of  the  main  rocker-arm  is  determined  by 
the  throw  of  the  main  eccentric,  and  the  rotation  of  the  small 
rocker-eccentric  is  determined  by  the  relative  position  of  the 
two  eccentrics  on  the  shaft.  Therefore,  in  proportion  as  the  main 
eccentric  is  advanced  toward  the 
crank  the  motion  of  the  rocker- 
eccentric  becomes  later  relative 
to  the  rocker  motion.  Now  the 
rocker-eccentric  may  be  placed  in 
any  desired  position  in  relation  to 
the  rocker,  and  it  may  be  so  put 
that  when  the  valve  is  cutting  off 
at  half-stroke  release  and  exhaust 
closure  will  be  timed  just  as  with  g'  33' 

an  ordinary  valve-gear ;  but  when  the  governor  eccentric  is 
moved  forward  the  rocker-eccentric  will  lag  behind  to  the  same 
extent,  and  the  whole  series  of  alternatingly  increased  and 
diminished  valve  movements  will  occur  a  little  later  in  the 
stroke.  The  effect  of  this  will  be  to  lengthen  the  interval  be- 
tween cut-off  and  release,  and  to  shorten  it  between  exhaust 
closure  and  admission ;  and  this  is  just  what  is  needed  in  order 
to  get  a  later  release  and  less  compression,  and  thus  the  ideal 
conditions  represented  in  Fig.  3 1  may  be  nearly  realized. 

Fig.  34  represents  an  indicator  diagram  from  the  Allfree 
engine.  It  will  be  recognized  as  a  remarkable  single-valve  dia- 
gram, and  further  comment  is  unnecessary. 


60 


THE   SLIDE-VALVE   AND   ITS  FUNCTIONS. 


The  valve,  Fig.  32,  is  in  the  shape  of  two  circular  segments  ; 
it  is  extremely  light,  and  is  balanced  between  an  arched  hood 
and  the  valve-seat.  Steam  is  admitted  to  the  inside  space,  and 
it  partly  surrounds  the  cylinder.  The  large  port-opening  obtain- 
able with  the  Allfree  valve-gear  obviates  the  necessity  of  com- 
plementary ports,  and  the  steam-passages  being  direct  and  very 
short,  the  clearance  is  reduced  to  a  minimum.  It  will  be  ob- 


Fig.  34. 

served  in  Fig.  32  that  the  weight  of  the  valve  is  carried  by  a 
long  adjustable  bracket  bearing,  which  keeps  it  from  bearing 
on  the  hood. 

This  valve-gear  may  be  used  on  any  single-valve  engine 
whether  steam  is  admitted  inside  the  valve  between  the  ports 
or  on  the  outside  ;  in  either  case  the  fixed  eccentric  will  be 
placed  in  line  with  the  crank  and  on  the  opposite  side  of  the 
main  eccentric. 


FOUR-VALVE   SYSTEMS.  61 


CHAPTER    III. 

FOUR-VALVE    SYSTEMS. 
INTRODUCTORY    REMARKS. 

FOUR  separate  valves  are  often  used,  two  at  each  end  ,of  the 
cylinder,  one  for  steam  and  one  for  exhaust.  If  all  four  valves 
were  positively  driven  by  one  eccentric  the  steam  distribution 
would  be  exactly  like  that  of  a  common  D-valve  —  it  would,  in 
effect,  be  the  D-valve  dissolved  in  its  four  component  parts. 
But  the  four-valve  system  has  points  of  superiority  not  possessed 
by  the  single  combination  valve. 

1.  Steam  and  exhaust  passages  become  short  and  direct. 

2.  The  valves  are  not  balanced  ;  but  the  unbalanced  pressure 
will  only  be  that  due  to  the  difference  between  the  pressure  in 
the  cylinder  and  that  in  the  adjoining  steam  and  exhaust  cham- 
bers, and  the  full  effect  of  this  will  be  intermittent,  and  on  the 
port  area  only. 

3.  The  separation  of  the  valves  makes  it  possible  to  reduce 
the  valve  motion  by  means  of  toggle  motion  of  the  valve  rods. 
The  port  must  be  covered  during  one-half  the  period  of  revolu- 
tion at  least,  and  if  the  motion  of  the  valve  is  the  same  in  oppo- 
site directions  from  a  central  position,  as  it  must  be  with  the 
D-valve,  the  greater  part  of  the  motion  must  generally  occur 
after  the  port  is  closed.     This  can  be  avoided  when  the  valves 
are  separate,  for  then  each  valve  may  be  separately  attached  to 
a  special  rocker  or  wrist-plate  in  a  manner  to  produce  a  reduced 
valve-motion  during  the  closed  period. 


62 


THE   SLIDE-VALVE   AND  ITS  FUNCTIONS. 


CORLISS    VALVES. 

Fig.  35  represents  diagrammatically  the  Corliss  valves  and 
wrist-plate  connections  for  one  end  of  the  steam  cylinder.  It 

shows  how  the  toggle 
motion  of  the  radius- 
rods  operates  to  shorten 
the  movement  of  the 
valve  after  the  port  is 
closed.  As  the  angular 
motion  of  the  valve  is 
reduced  by  the  toggle 
action,  it  becomes  pos- 
sible to  use  smaller 
valves  than  otherwise 
practicable,  because  -a 
given  angular  motion 
yields  a  larger  p'ort- 
opening  than  could  be 

had  with  a  straight  mo- 
tion  of  the  rode 

Figs.  36  and  37  show  the  construction  of  the  first  Corliss 
valves.  The  valve  stem  has  a  flat  extension  which  fits  the 
whole  length  of  the  valve,  and  has  a  journal  at  each  end. 

The  Corliss  steam- 
valve,  shown  in  Fig.  38, 
is  a  simple  circular  slide 
suitably  guided.  The  slide 
and  cylindrical  parts  at 
each  end  are  now  often 
cast  in  one  piece,  and  the 


35- 


Figs.  36  and  37. 


valve-stem   terminates  in  a  T-head  which  fits-  in  a  slot  across 
the  end  of  the  cylindrical  part. 

These  valves  are  often   made  double-ported  to  avoid    the 


FO  UR-  VA  L  VE   S  YS  TEMS. 


necessity  of  using  large  diameters  or  to  reduce  the  motion. 
The  objection  to  double  ports  is  the  increased  clearance  space 
they  make.  The  clearance  may  be  re- 
duced to  a  minimum  by  putting  the 
valves  in  the  cylinder  heads,  and .  this 
would,  no  doubt,  become  the  general 
practice  if  it  did  not  involve  somewhat 
complicated  steam  connections. 

Double-ported  steam  and  exhaust 
valves  are  shown  in  Fig.  39.  Fig.  40 
represents  three-ported  valves  for  the 
lower  head  of  a  6o-inch  low-pressure  cyl- 


Fig.  38. 


inder  of  a  cross-compound  vertical  engine,  designed  by  Messrs. 
Rice  &  Sargent.     The  steam-valve  is  held  up  to  its  seat  by  end- 


Fig.  39- 


64 


'THE  SLIDE-VALVE   AND   ITS  FUNCTIONS. 


gibs,  supported  by  flat  steel  springs,  and  these  are  adjustable  by 
means  of  screws  from  the  outside. 

The  exhaust-valve  is  a  hollow  shell  with  closed  ends.  It  is 
separated  from  the  bottom  Of  the  cylinder  by  a  loose  ported 
valve-seat  plate,  the  upper  side  of  which  is  flush  with  the  cylin- 
der head.  This  plate  is  held  freely  between  planed  jaws  in  the 
cylinder  head  ;  and  the  steam  pressure  in  the  cylinder  keeps  it 
against  the  valve,  and  prevents  the  steam  from  passing  inside 
the  valve  when  the  ports  are  closed.  The  opposite  side  of  the 
valve  is  provided  with  a  single  wide  port,  and  is  always  open  to 
the  exhaust-chest.  This  construction  gives  less  clearance  than 
the  ordinary  Corliss  exhaust  valve. 


Fig.  40. 

The  operation  of  the  Corliss  induction  valve  is  quite  different 
from  that  of  a  common  slide-valve.  The  special  feature  is  a 
disconnecting  device,  which  allows  the  valve  to  be  closed  by  a 
spring  or  vacuum  d»sh-pot,  or  other  independent  agency.  The 
eccentric  moves  the  valve  till  it  is  released  .by  the  knock-off 
cam,  and  it  is  then  closed  by  the  dash-pot.  The  valve  is  per- 
fectly at  rest  during  the  expansion  period  and  the  greater  part 
of  the  exhaust  period,  but  during  the  exhaust  period  it  is  caught 
by  the  "  steam-hook,"  and  slowly  started,  so  as  to  admit  steam 
near  the  beginning  of  the  forward  stroke.  The  amount  of 
opening  and  the  period  of  admission  depend  on  the  ppsition  of 
the  knock-off  cam,  and  this  is  in  turn  determined  by  the  speed- 


FOUR-VALVE   SYSTEMS.  65 

regulator.  When  the  steam-hook  arm  strikes  the  knock-off  cam 
the  hook  is  released,  and  the  valve  is  closed  by  the  dash-pot. 
The  result  is  a  nearly  ideal  valve-motion. 

LIMITATIONS    OF    THE    CORLISS    GEAR. 

When  a  single  eccentric  drives  both  steam  and  exhaust  valves 
the  range  of  cut-off  is  limited  to  about  half  the  piston-stroke. 
This  will  become  obvious  by  considering  the  following  necessary 
conditions : 

1.  After  the  eccentric  has  reached  the  extreme  of  its  throw 
in  either  direction  all  valve-gear  motions  are  reversed. 

2.  The  steam-valve  must  be  released  before  the  oceentric- 
motion  is  reversed,  for  if  the  hook  does  not  strike  the  knock-off 
cam  during  the  forward  motion  it  cannot  strike  it   during  its 
return  motion. 

3.  The  maximum  exhaust    opening,   or  the  middle  of  the 
exhaust  period,  must  occur  when  the  eccentric  is  at  the  end  of 
its  throw. 

Now,  in  order  to  get  release  of  the  expanded  steam  in  the 
cylinder  before  the  commencement  of  the  return-stroke  and 
exhaust-closure  a  little  before  the  end  of  .the  return-stroke,  the 
middle  of  the  exhaust  period,  or  the  extreme  throw  of  the  ec- 
centric must  evidently  occur  before  the  middle  of  the  return- 
stroke  ;  and  therefore  the  extreme  throw  of  the  eccentric  in  the 
opposite  direction  must  occur  before  the  middle  of  the  forward 
stroke,  and  the  valve  must  be  released  before  that  point  is 
reached,  if  released  at  all. 

The  point  where  steam  is  cut  off  is  not  coincident  with  the 
.action  of  the  cut-off  cam,  for  it  takes  some  time  to  close  the 
valve.  With  a  long  piston-stroke  the  closing  period  is  compara- 
tively short,  but  it  is  far  from  being  "instantaneous,"  as  seems 
to  be  the  prevalent  impression.  The  return-motion  of  the  valve 
.and  dash-pot  starts  comparatively  slow,  as  indeed  all  motion  does  ; 
but  this  slow  motion  is  not  observable  on  account  of  the  short- 


66  THE   SLIDE-VALVE  AND   ITS  FUNCTIONS. 

ness  of  the  interval,  and  by  overlooking  this  fact  a  false  concep- 
tion of  the  dash-pot  action  is  formed. 

A  good  vacuum  dash-pot  closes  the  valve  in  about  one-six- 
teenth of  a  second  at  late  cut-off,  or  during  one-twelfth  of  a 
revolution  if  the  engine  makes  eighty  revolutions  per  minute ; 
and  the  closing  motion  will  in  that  case  cover  about  one-sixth  of 
the  stroke.  With  short  stroke  and  high  piston-speed  the  latest 
cut-off  would  be  much  later  than  mid-stroke. 

The  releasing  gear  is  seldom  used  on  high-speed  engines,  be- 
cause the  sudden  and  frequent  action  will  cause  it  to  wear  quick- 
ly and  become  unreliable ;  and,  as  a  sharp  cut-off  is  not  attainable 
at  high  speed,  there  is  not  sufficient  justification  for  the  use  of  a 
somewhat  complex  and  delicate  gear.  One  hundred  revolutions 
per  minute  may  be  assumed  as  a  practical  limit  for  the  Corliss 
gear. 

This  speed-limit  of  the  Corliss  gear  is  of  no  consequence  in 
connection  with  large  engines,  where  great  piston-speed  may  be 
obtained  with  less  than  one  hundred  revolutions  per  minute ; 
and,  for  obvious  reasons,  in  such  cases  simplicity  or  fewness  of 
parts  is  a  consideration  of  less  moment. 

It  will  be  understood  from  the  foregoing  that  late  release  and 
late  exhaust  closure  are  conditions  imposed  by  the  single-eccen- 
tric-valve gear ;  and  these  conditions  agree  very  well  with  moderate 
piston  speed,  but  at  higher  speed  earlier  release  and  more  com- 
pression may  be  required. 

This  may  be  effected  by  moving  the  eccentric  forward  on 
the  shaft ;  but  the  reversing  of  the  steam-hook  motion  would  then 
also  occur  at  an  earlier  stage  of  the  forward  stroke,  and  the  range 
of  cut-off  would  be  correspondingly  shortened. 

Earlier  exhaust  closure  could  be  had  by  giving  the  exhaust- 
valve  more  lap,  but  this  would  involve  a  later  release  of  the  ex- 
panded steam  at  the  end  of  the  forward  stroke.  On  the  other 
hand,  shortening  the  exhaust-lap  would  give  earlier  release,  but 
insufficient  or  no  compression. 


EO  UR-  VAL  VE   S  YS  TEATS. 


67 


THE    SINGLE-ECCENTRIC    VALVE    DIAGRAM. 

Let  the  circle,  Fig.  41,  represent  the  path  of  the  center  of  the 
eccentric  turning  in  the  direction  shown  by  the  arrow,  and  let 
the  horizontal  diameter  represent  the  throw  of  the  eccentric. 
When  the  center  of  the  eccentric  is  at  point  I  the  steam-port 
opens,  and  if  the  valve  is  not  released  before  the  end  of  the 
throw  at  point  3,  the  port  will  close  again  at  point  4.  The 
exhaust-port  opens  at  point  6,  and  is  closed  at  point  9.  The 
crank  is  supposed  to  be  at  its  dead  center  C  when  the  eccentric 
is  at  point  2,  just  after  opening  the  steam-port.  When  the  crank 
is  on  the  opposite  dead  center,  the  eccentric  must  be  at  point 
7,  diametrically  opposite  point 
2  ;  and  the  point  of  release  at 
6  occurs  a  little  before  this, 
as  it  should  do.  Arc  1-2 
represents  period  of  steam- 
lead,  and  arc  6-7  represents 
period  of  exhaust-lead,  and  arc 
9-1  represents  the  compres- 
sion period.  When  the  ec- 
centric is  at  point  3,  the  valve- 
gear  motion  is  reversed,  and 
the  crank  has  not  yet  arrived  at  point  10  ;  the  valve  is,  there- 
fore, necessarily  released  before  mid-stroke,  if  it  is  released  at 
all.  Note  that  the  chords  must  be  parallel  if  there  is  only 
one  eccentric,  and  that  in  order  to  get  release  before  the  end 
of  the  stroke,  the  diameter  2—7  must  cross  the  chord  6—9.  If, 
in  order  to  extend  the  cut-off,  point  2  be  moved  back  to  point 
10,  the  diameter  10-5  could  not  be  made  to  cross  the  exhaust 
chord  in  any  position,  and  release  would  then  take  place  after 
commencement  of  the  return  stroke.  This  simple  diagram  fully 
illustrates  the  limitations  of  the  single-eccentric  valve-gear ;  but 
it  may  be  profitable  to  turn  the  figure,  and  let  diameter  2-7 


68  THE  SLIDE-VALVE   AND   ITS  FUNCTIONS. 

represent  stroke  of  the  piston,  and  let  the  circle  represent 
the  path  of  the  crank.  Points  I,  2,  3,  ...  will  then  mark  sig- 
nificant positions  of  the  valve-gear  in  proper  relation  to  the 
piston-stroke,  and  an  imaginary  indicator-diagram  may  be  con- 
structed, as  shown.  Note  that  by  this  arrangement  the  position 
of  the  eccentric  relative  to  the  crank  is  not  considered  ;  but  it 
clearly  shows  the  result  when  the  eccentric  is  moved  forward  on 
the  shaft,  in  which  case  the  whole  cycle  of  events  occurs  earlier 
in  the  stroke  ;  that  is,  the  lead  is  increased,  the  range  of  the  cut- 
off is  diminished,  and  there  will  be  earlier  release  and  more  com- 
pression. 

The  steam-hook  connects  with  the  valve  at  or  near  the 
extreme  of  its  throw ;  and  the  eccentric-motion  8-1  determines, 
therefore,  to  what  extent  the  valve  must  overlap  the  steam-edge 
of  the  port  when  at  rest.  Note  that  during  this  period  the  valve 
should  move  as  little  as  possible  (8-1  Fig.  36),  and  the  radius- 
rod  must  therefore  have  considerable  lateral  motion  before  the 
valve  opens. 

When  the  wrist-plate  is  in  its  central  position  the  eccentric  is 
at  point  10,  and  the  lap  of  the  steam-valve  in  this  position  is  de- 
termined by  the  qccentric-motion  10— i.  The  corresponding 
exhaust-lap  is  determined  by  the  eccentric-motion  5-6.  The  ex- 
haust-chord 9—6  could  evidently  be  moved  to  the  other  side  of  the 
center,  in  which  case  the  exhaust -valve  would  not  cover  the  port 
at  half -throw  ;  or  the  chord  could  be  placed  centrally, -which  would 
make  the  exhaust-period  cover  exactly  one-half  revolution,  and 
would  put  the  exhaust-edges  "line  and  line"  in  the  half -throw 
position ;  but  such  changes  would  give  earlier  release  and  less 
compression.  Lap  or  clearance  can  be  laid  out  very  accurately 
on  the  drawing-board,  and  it  should  be  marked  on  the  drawing. 
The  great  adjustability  of  the  Corliss  gear  makes  it  easy  to  set 
the  lap  by  some  rule  of  thumb  after  the  engine  is  erected,  and  a 
little  variation  in  the  points  of  release  and  compression  may  not 
be  of  much  practical  consequence  ;  but  when  a  "good  "  indicator- 


FOUR-VALVE   SYSTEMS.  69 

card  is  required  there  may  later  be  some  tedious  resetting  to  do. 
There  should  always  be  marks  at  the  end  of  the  valve,  inside 
the  rear-bonnet,  in  line  with  the  steam-edges  of  valve  and  valve- 
seat. 

At  point  3  the  motion  of  the  steam-hook  is  reversed  ;  and  if 
arc  3-P  represents  the  period  of  dash-pot  movement,  arc  2-P 
will  represent  the  admission-period  for  latest  cut-off,  as  deter- 
mined by  the  knock-off  cam,  which,  in  this  case,  would  be  one- 
quarter  of  a  whole  revolution  or  half  of  the  piston-stroke ;  but  if 
under  heavy  load,  the  speed-regulator  puts  the  knock-off  cam  out 
of  reach  of  the  steam-hook,  the  engine  will  take  steam  during 
period  1-4,  or  nearly  full  stroke. 

TWO    ECCENTRICS. 

In  order  to  obtain  a  greater  range  of  cut-off  in  Corliss 
engines,  a  separate  steam-eccentric  is  used  and  has  become  quite 
common.  With  two  eccentrics  the  admission  and  exhaust-peri- 
ods can  be  adjusted  independently,  and  steam  may  be  cut-off 
anywhere,  nearly  to  the  end  of  the  stroke. 

In  order  to  start  the  valve  without  shock,  the  hook  must 
connect  with  it  when  near  the  end  of  its  throw ;  and  the  steam- 
eccentric  may  be  so  placed  in  relation  to  the  crank,  that  this 
connection  is  made  near  the  end  of  the  return  piston-stroke,  for 
the  valve  need  not  overlap  the  port  more  than  from  one-half  to 
three-fourths  of  an  inch  when  closed. 

The  arrangement  of  steam-rods  exemplified  in  Fig.  35, 
is  in  every  respect  satisfactory  in  connection  with  a  single- 
eccentric  valve-gear  ;  for  in  that  case  a  slow  initial  valve-motion 
is  imperative,  and  it  is  obtained  by  the  lateral  movement  of  the 
radius-rod.  But  with  two  eccentrics  a  quicker  initial  motion  is 
feasible  and  desirable,  and  it  may  be  obtained  by  reversing  the 
valve-motion  and  admitting  steam  over  the  top  of  the  valve 

(Fig.  39). 

Separate  eccentrics  require  separate  wrist-plates,  and  their 


TO 


THE   SLIDE-VALVE  AA'D   ITS  FUNCTIONS. 


centers    may  be    located    one   above   the    other,   as    shown    in 

Fig.   39- 

Figs.  42  and  43  show  how  the  eccentrics  may  be  placed  on 
the  shaft.  The  steam-eccentric  is  at  point  2,  Fig.  42,  and  the 
exhaust-eccentric  is  at  point  E,  Fig.  43,  and  the  crank  is  at  its 
dead  center  at  C.  Individual  eccentric  circles  are  shown  for 
the  sake  of  clearness,  and  the  notation  is  the  same  as  in  Fig.  41. 
An  imaginary  motion  of  the  eccentric-arm  will  point  out  the 
various  events.  Referring  to  Fig.  42,  near  point  8,  •  at  the 
extreme  of  the  throw,  the  hook  connects  with  the  steam-valve, 
and  at  point  I  the  steam  edges  are  on  the  point  of  separating, 
and  the  eccentric-motion,  8-1,  determines,  therefore,  the  initial 


American  JToeMiiM 

Fig.  43- 

valve-motion.  When  the  eccentric  is  at  point  2  the  crank  is  at 
its  dead  center,  as  shown.  At  point  10  the  steam-wrist-plate  is 
in  its  central  position,  and  in  that  position  the  valve  does  not 
cover  the  port,  as  with  the  single-eccentric  gear ;  but  the  port  is 
open  to  a  certain  extent,  determiaed  by  the  eccentric-motion 
i-io.  Point  3  marks  the  extreme  of  the  throw,  and  the  corre- 
sponding position  of  the  crank  is  at  C',  at  about  three-quarters 
of  the  piston-stroke,  and  the  limit  of  automatic  cut-off  is  a  little 
later.  If  the  hook  does  not  strike  the  knock-off  cam  the  valve 
will  remain  open  till  closed  by  the  return  stroke  of  the  eccentric 
at  point  4,  near  the  middle  of  the  return  piston-stroke. 

The  exhaust  action  is  discernible  from  Fig.  43.      It  is  simi- 
lar to  the  single-eccentric  action,  but  with  this  difference,  that 


FOUR-VALVE   SYSTEMS.  71 

the  release,  at  point  6,  occurs  at  about  90  per  cent  of  the  pis- 
ton-stroke, and  the  exhaust  is  cut  off  at  about  70  per  cent  of 
the  return-stroke,  at  point  9.  The  motion  of  the  exhaust -valve, 
after  it  has  closed  the  port,  is  determined  by  the  eccentric- 
motion  9-3-6,  and  full  port-opening  is  obtained  by  the  eccen- 
tric-motion 6-8.  The  motion  9-10  determines  the  exhaust-lap 
when  the  wrist-plate  is  in  its  central  position. 

A  valve-gear  designed  to  be  operated  by  a  single-eccentric 
cannot  very  well  be  made  to  cut  off  much  later  than  at  half- 
stroke,  even  when  a  separate  exhaust  eccentric  is  added.  For 
the  slow  initial  valve-motion  requires  at  least  half  the  throw  of 
the  eccentric,  and  the  other  half  is  not  sufficient  for  a  late  cut- 
off ;  and  it  will  readily  be  seen  from  an  inspection  of  Figs.  35 
and  39  that  a  quicker  initial  valve-motion  in  Fig.  35  would  in- 
volve radical  changes  in  the  valve-gear.  However,  the  range  of 
cut-off  may  be  increased  some  by  moving  the  eccentric  back, 
sacrificing  the  lead  ;  and  to  this  there  is  no  objection  when  it 
does  not  involve  later  release. 

The  advantage  gained  by  a  second  eccentric  would  consist 
in  more  compression  and  earlier  release. 

CORLISS    VALVE    DIMENSIONS. 

The  steam-  and  exhaust-ports  of  Corliss  engines  are  usually 
made  as  long  as  the  diameter  of  the  cylinder-bore,  and  steam- 
and  exhaust-valves  are  usually  of  equal  diameters,  but  these 
diameters  do  not  vary  as  the  bore  of  the  cylinders,  as  might  be 
anticipated.  The  proportion  varies  from  one-third  of  the  bore 
in  small  engines  to  one-sixth  for  large  low-pressure  cylinders. 
The  port  is  not  necessarily  proportioned  according  to  the  diam- 
eter of  the  valve,  but  the  port-opening  will  be  nearly  so.  It  is 
considered  a  safe  rule  to  make  the  width  of  port  sufficient  to 
allow  a  mean  velocity  of  8000  feet  per  minute  of  the  enter- 
ing steam,  and  6000  feet  per  minute  of  the  exhaust  ;  but  a 
smaller  port  area  may  consistently  be  allowed  for  large  cylin- 


72  THE  SLIDE-VALVE   AND   ITS  FUNCTIONS. 

ders.      The  port-opening  is  in  proportion  to  the  travel  of  the 
valve,  which  is  practically  limited  by  the  diameter. 

DIRECTIONS    FOR    SETTING    THE    VALVE-GEAR. 

Adjust  length  of  eccentric-rods  to  give  wrist-plate  equal 
travel  on  both  sides  of  center-mark  on  bracket.  Adjust  length 
of  radius-rods  to  give  proper  lap  with  wrist-plate  in  its  central 
.position.  Move  wrist-plate  to  end  of  its  travel  either  way  (as 
marked  on  the  bracket),  and  adjust  length  of  drop-rods  to  let 
the  hooks  freely  engage  the  catch-blocks.  Put  crank  on  dead 
centers,  and  set  eccentric  ahead  of  the  crank,  sufficiently  to  give 
the  proper  lead.  Raise  governor  to  highest  working  position, 
and  adjust  length  of  rods  so  that  the  knock-off  cams  will  just 
keep  1?he  hooks  off  the  catch-blocks ;  or  some  initial  motion 
may  be  allowed,  but  not  enough  to  open  the  port. 

VALVES    OF    THE    PORTER— ALLEN    ENGINE. 

An  interesting  instance  of  the  four-valve  system  is  found  in 
the  Porter-Allen  engine.  There  are  two  steam-valves  on  one 
side  of  the  cylinder,  and  two  exhaust-valves -.on  the  other  side, 
and*  the  valves  move  in  a  direction  parallel  with  the  cylinder- 
bore.  The  valves  are  flat ;  and  the  steam-pressure  on  opposite 
valve-faces  is  absolutely  balanced  by  means  of  pressure-plates 
which  fit  closely  against  the  back  of  the  valve,  and  the  steam- 
passages  to  and  from  the  cylinder  are  short  and  direct.  The 
valves  are  driven  by  an  Allen  link,  and  the  position  of  the 
link-block  is  automatically  changed  by  a  Porter  governor.  The 
period  of  admission, is  changed  by  varying  the  travel  of  the 
valve,  while  the  lead  remains  constant ;  and  the  result  is  the 
same  as  what  may  be  accomplished  by  a  shifting  eccentric  and 
a  shaft  governor.  The  exhaust-valves  are  driven  from  a  fixed 
point  on  the  link,  and  they  have  an  invariable  motion,  precisely 
as  the  motion  derived  directly  from  an  eccentric  fixed  on  the 
engine-shaft.  The  steam  valves  have  separate  valve-stems  ;  and 


FOUR-VALVE  SYSTEMS. 


they  receive  their  motion  from  two  bell-crank  levers,  which,  like 
the  Corliss  wrist  motion,  greatly  reduce  the  movement  of  the 
valve  after  it  has  closed  the  port. 

Fig.    44    shows  a   horizontal   section    through   cylinder   and 
valves  ;  and  it  shows  the  course  of  the  steam  through  four  open- 


74  THE   SLIDE-VALVE   AND   ITS  FUNCTIONS. 

ings  into  the  steam-port,  and  also  from  the  exhaust -port  into  the 
exhaust-chest.  The  pressure-plates  are  arched  so  as  to  make 
them  practically  unyielding  to  steam-pressure,  and  there  is  left 
a  free  passage  for  steam  through  the  opening  of  the  arch.  The 
pressure-plates  of  the  admission-valves  are  adjustable  to  more 
or  less  close  contact  with  the  valve  by  means  of  short  inclines, 
against  which  they  are  held  by  the  steam-pressure  in  the  steam- 
chest.  They  are  adjusted  by  a  short  lateral  displacement  on 
said  inclines  by  means  of  screws,  which  extend  through  the  bot- 
tom of  the  steam-chest.  The  pressure-plates  of  the  exhaust- 
valves  are  bolted  to  their  seats.  The  valves  are  formed  like 
open  rectangular  frames  ;  and  the  opening  in  the  frame  is  made 
wide  enough  to  reach  the  edge  of  the  valve-seat  when  the  port 
opens,  otherwise  there  would  not  be  four  simultaneous  port- 
openings.  The  space  inclosed  by  the  valve-frame  adds  to  the 
cylinder  clearance ;  and  as  the  valve  is  perfectly  balanced  the 
main  object  of  the  bell-crank  levers  is,  apparently,  to  shorten  the 
valve  and  limit  the  clearance  space.  As  the  steam-valves  do 
not  move  in  unison,  each  valve  must  have  its  individual  valve- 
stem,  the  stem  of  the  rear  valve  passing  through  the  front  valve. 
The  exhaust-valves  have  no  lap  ;  that  is,  in  its  central  position 
the  exterior  edge  of  port  and  valve  are  "line  and  line."  The 
valve,  therefore,  opens  and  closes  quickly,  and  only  a  short  travel 
is  required.  It  is  obtained  by  means  of  a  double-ended  redu- 
cing-rocker,  from  the  short  arm  of  which  motion  is  imparted 
directly  to  both  exhaust-valves. 

Fig.  45  shows  one  of  the  exhaust -valves  used  on  the  first 
Porter-Allen  engine.  There  is  no  pressure-plate ;  but  an  open 
frame,  of  nearly  same  size  as  the  valve-frame,  is  held  against  the 
back  of  the  valve,  as  shown.  This  frame  is  bolted  to  a  copper 
diaphragm,  which  is  clamped  to  the  steam-chest  cover  ;  and  the 
steam  from  the  cylinder,  having  access  to  the  back  of  this  dia- 
phragm, keeps  the  frame  against  the  valve  and  holds  it  to  its 
seat.  During  the  exhaust  period  this  valve  is  absolutely  bal- 


FOUR-VALVE  SYSTEMS. 


75 


anced ;  and  the  pressure  during  the  admission  period,  when"  a 
tight  joint  is  needed,  is  not  excessive.  There  is  a  projection  on 
the  chest-cover,  which  nearly  fills  the  space  inside  the  valve- 
frame,  and  thus  the  clearance  was  reduced  as  much  as  pos- 
sible. 


Fig.  45- 

The  valves  and  valve-gear  of  this  engine  are  the  invention  ot 
John  F.  Allen,  and  in  the  history  of  engineering  will  hold  a 
prominent  position,  not  only  on  account  of  their  originality  and 
excellency,  but  because  they  first  made  high  speed  in  a  variable 
cut-off  engine  practicable. 


GRIDIRON    VALVES. 

Flat  multiported,  or  "gridiron"  valves,  Fig.  47,  are  often 
employed  as  a  means  of  obtaining  sufficient  port-opening,  by 
short-valve  travel,  ancl'they  have  lately  been  extensively  used 
on  four-valve  engines.  Flat  valves  are  better  adapted  for  multi- 
porting  than  Corliss  valves.  They  give  straight  steam-passages, 
and  they  can  readily  be  fitted  with  removable  seats  of  hard, 
close-grained  iron ;  which  is  of  some  importance  for  high-duty 
engines  under  high  steam-pressure,  and  the  accurate  spacing 
and  finishing  of  the  ports  is  more  readily  obtainable  than  with 


76 


7 HE  SLIDE-VALVE  AATD   ITS  FUNCTIONS. 


valve-seats  cast  on  the  cylinder.  These  valves  have  also  con-, 
siderable  bearing  surface,  equally  distributed,  and  they  can  be 

forced  from  their  seat 
when  much  water  is  car- 
ried into  the  cylinder. 
Some  offset  to  these  ad- 
vantages is  found  in  the 
fact  that  the  bars  of  the 
exhaust-valve  and  the 
steam-valve-seat  expose 
considerable  sin  face  to  the 
entering  steam.  The  short 
travel  of  multiported  valves 
Fig.  46.  The  Hill  Valves.  is  an  advantage,  if  not  a 

necessity.  It  is  also  a  matter  of  convenience,  for  it  provides 
for  a  valve  operating  mechanism  of  practical  construction  and 
of  moderate  proportions. 

THE    HILL    VALVES. 

A  unique  combination  of  gridiron  valves,  designed  by  Mr. 
Edward  K.  Hill,  is  represented  in  Figs.  46  and  47.     The  main 


Fig.  47- 

characteristics  of  this  system  is  apparent  from  Fig.  46,  which 
represents  a  cross-section  through  a  pair  of  valves  and  valve- 
seats.  A  is  the  inlet-valve,  which  controls  the  admission  and 


FOUR-VALVE   SYSTEMS  77 

cut-off,  and  13  is  the  exhaust -valve.  Both  valves  are  seated  in  a 
round,  open  cast-iron  plug,  of  a  hard,  close-grained  mixture,  of 
which  Fig.  47  is  a  longitudinal  section,  exposing  the  face  of  the 
exhaust-valve.  The  plug  containing  the  valves  is  pushed  in 
endwise,  and  is  kept  in  place,  by  a  single  nut,  as  shown  ;  and  it 
maybe  removed  and  replaced  very  quickly  —  a  feature  which, 
practical  e-nginemen  will  appreciate.  The  valve-moving  mechan- 
ism (not  shown)  is  attached  to  the  front  end  of  the  plug,  and 
contains  a  pair  of  toggle-levers,  by  which  the  exhaust -valve  is 
moved  endwise,  and  which  leave  it  nearly  stationary  between 
the  exhaust  periods.  The  inlet -valve  is  worked  by  an  oscillating 
pusher,  which  engages  an  adjustable  tappet  on  the  valve-stem. 
The  pusher  is  below  the  valve-stem  ;  and  at  a  certain  point  of  its 
forward  and  downward  movement  it  leaves  the  tappet,  and  the 
valve,  being  released,  is  quickly  closed  by  a  helical  spring  assisted 
by  the  steam-pressure  on  the  valve-stem.  The  point  of  cut-off 
is  changed  by  vertical  adjustment  of  the  tappet,  and  which  is 
accomplished  automatically  by  a  concave  lifting  cam,  operated 
by  the  governor.  To  prevent  concussion  by  the  closing  of  the 
-  valve,  there  is  a  dash-pot  in  the  head  end  of  the  bracket,  at  the 
end  of  the  valve-stem.  It  will  be  observed  that  this  combination 
embodies  the  fundamental  principles  of  the  Corliss-gear,  though 
there  is  no  apparent  similarity  in  the  construction.  The  valves 

—  one  pair  at  each  end  of  the  cylinder  —  are  driven  from  eccen- 
trics on  a  revolving  shaft,  which  runs  alongside  the  cylinder,  and 
which  also  drives  the  governor.  There  is  an  eccentric  for  each 

alve ;  and  the  range  of  cut-off  is,  therefore,  not  restricted  in 
any  degree,  and  the  adjustability  for  lead,  release,  and  compres- 
sion is  practically  unlimited.  The  peculiar  releasing  mechan- 
ism and  the  short  travel  make  a  speed  of  1 50  revolutions  per 
minute  practicable. 

The  peculiar  construction  of  these  valves  permits  of  both 
valves  being  placed  directly  under  the  cylinder,  which  makes 
less  clearance  than  with  two  separate  steam-passages  at  each 


78 


THE   SLIDE-VALVE   AND   ITS  FUNCTIONS. 


end  of  the  cylinder  ;  and  this  location  of  valves,  affords  a  nat- 
ural drainage  from  the  cylinder ;  and  the  steam  inlet,  acting 
somewhat  like  a  separator,  will  serve  to  precipitate  the  water. 
Being  stowed  between  the  valve-seats,  it  is  left  in  position  to 
be  swept  away  by  the  exhaust  without  entering  the  cylin- 
der. It  can  hardly  be  disputed  that  the  proper  place  for  the 
valves  is  directly  below  the  cylinder-bore ;  and  it  is,  no  doubt, 
practical  difficulties  which  have  prevented  such  disposition  of 
the  valves  from  becoming  more  general.  The  system  here  de- 
scribed apparently  solves  the  problem  without  a  drawback  ;  for 
the  valves  are  readily  accessible  without  any  bolted  joints,  and 
there  is  no  interference  with  steam-  and  exhaust-passages. 

According  to  the  builders,  this  system  is  the  outgrowth  of 
the  Wheelock  system,  which  it  has  now  entirely  superseded  ;. 
and  a  comparison  of  the  two  systems  becomes,  therefore  of 
great  interest. 

THE    WHEELOCK    VALVES. 

Originally  these  valves  were  cylindrical  and  semi-rotative 
like  the  Corliss  valves ;  but  there  is  a  rational,  functional  differ- 
ence. In  the  Wheelock  system  one  valve  serves  for  admission 

and  release,  and  a  smaller 
valve,  in  close  proximity  to 
this,  cuts  off  the  steam  at  a 
point  determined  by  the 
governor ;  and  in  that  re- 
spect the  system  differs 
from  all  others  described  so 
far,  and  it  belongs  properly 


Fig.  48.    The  Wheelock.  A 

the    following    chapter.       These 

hardened  steel  trunnions  in  hard  bushings,  which  partly  relieved 

the  pressure  on  the  valve-seat ;    and  the  valve  being  tapered, 


in   the   independent  cut-off 
system,    fully    discussed   in 
valves    were    supported    by 


FOUR-VALVE   SYSTEMS.  79 

the  working  faces  were  brought  into  close  proximity  by  proper 
end-adjustment.  Under  moderate  steam-pressure  the  contact 
will  be  light ;  but,  obviously,  this  mode  of  balancing  is  not  satis- 
factory under  very  high  pressure,  for  the  valve  being  supported 
at  the  ends  only,  the  deflection  in  the  center  will  cause  it  to 
bear  hard  on  the  valve-faces ;  and  as  the  valve-barrel  cannot 
readily  be  lined,  the  wear  of  the  central  portion  may  become 
quite  considerable.  x 

Fig.  48  represents  a  section  through  the  valves.  A  is  the 
main  valve,  and  B  is  the  cut-off  valve  or  wiper.  It  will  be  no- 
ticed that  the  main  valve  has  a  large  exhaust- cavity,  and  is  really 
a  cylindrically  formed  D-valve.  The  exhaust -cavity  greatly 
increases  the  unbalanced  area,  and  it  weakens  the  valve-body ; 
and  the  travel  becomes  considerable  compared  with  the  width 
of  the  bearing-surfaces.  The  cut-off  valve  has  a  cavity  for 
double  admission.  It  is  worked  from  the  main-valve  lever  by 
means  of  a  Corliss  crab-jaw,  and  it  is  closed  by  a  tripping- 
mechanism  under  control  of  the  governor,  similar  to  that  of  the 
Corliss  engine  ;  and  the  limitations  imposed  by  this  gear  are  the 
same  as  those  of  the  single-eccentric  Corliss  gear.  This  is 
probably  the  only  engine  which  has  an  independent  cut-off  valve 
worked  by  a.  Corliss  releasing-gear. 

As  the  advantage  of  higher  steam  pressure  became  apparent, 
the  inventor,  Mr.  Jerome  Wheelock,  changed  his  valves  into 
gridiron  valves,  which  he  seated  in  skeleton  plugs. 

These  valves,  unlike  the  Hill  valves,  were  actuated  sidewise 
by  an  inside  rocker- shaft  and  cranks. 


80        •'"        THE  SLIDE-VALVE   AArD  ITS  FUNCTIONS. 


CHAPTER    IV. 

INDEPENDENT    CUT-OFF. 
INTRODUCTORY    REMARKS. 

IT  has  been  explained  in  Chapter  I.  how  the  exhaust  may 
be  satisfactorily  regulated  by  separating  the  exhaust-valve  from 
the  admission-valve.  Better  results  can  be  obtained  by  having 
two  valves,  one  of  which  controls  the  admission  and  exhaust, 
while  the  other  controls  the  cut-off  only ;  for  by  such  arrange- 
ment larger  port -opening  and  sharper  cut-off  is  obtainable,  while 
the  points  of  lead  release  and  compression  are  fixed.  The  use- 
fulness of  this  arrangement  is  somewhat  limited,  however,  by 
the  fact  that  ample  compression  and  a  wide  range  of  cut-off  can- 
not exist  at  the  same  time ;  but  this  limitation  would  only  be 
of  consequence  in  "high-speed"  engines  having  considerable 
"clearance." 

Cut-off  valves  are  slide-valves  whose  only  function  is  to  cut 
off  the  connection  between  the  steam  in  the  cylinder  and  that 
in  the  steam-chest  before  the  piston  has  completed  its  stroke. 

In  England,  and  on  the  Continent,  they  are  named  Expansion 
Valves,  because,  by  cutting  off  the  cylinder-steam  from  the 
main  steam  supply,  they  provide  for  expansion  of  the  steam  in 
the  cylinder.  When  these  valves  came  into  use  there  were  no 
single-valve  automatic  cut-off  engines  made,  and  effective  expan- 
sion was  obtained  by  expansion-valves  only. 

The  cut-off  valve  is  auxiliary  to  the  main  valve  ;  it  opens  and 
closes  a  port  through  which  the  steam  must  pass  before  it 
enters  the  main  steam-port,  or  cylinder-port.  The  function 
of  the  main  valve  is  to  admit  and  exhaust  the  steam  through 


INDEPENDENT  CUT-OFF. 


81 


the  main  ports,  and  it  determines  the  points  of  admission,  re- 
lease, and  exhaust  closure.  The  only  absolute  requirements  of 
the  cut-off  valve  are,  that  it  shall  open  each  of  the  auxiliary 
steam-ports  not  later  than  the  commencement  of  each  piston- 
stroke,  that  it  shall  close  it  again  at  a  certain  point  in  the  stroke 
-  which  may  be  varied  by  hand,  or  automatically  changed  by 
the  governor,  —  and  lastly  that  it  shall  not  open  for  steam  again 
before  the  main  valve  has  closed  the  cylinder-port. 

THE  CUT:OFF  VALVE  ON  A  STATIONARY  VALVE-SEAT. 

Fig.  49  shows  the  Gonzenbach  cut-off.     The  cut-off  valve 
slides  on  a  ported  partition  above  the  main  valve  ;  and  the  steam, 
after  passing  into  the  lower  steam-chest,  is  admitted  through 
either     one     of     the 
cylinder-ports    which 
happens    to     be     open. 
This    cut-off     valve     is 
double-acting  —  it    cuts 
off  by  both  port  edges, 
moving    in    opposite  di- 


rections—  for    there 

must  be  one  cut-off  for  Fig'  49'    The  Gonzenbach  Valve. 

each  stroke  of  the  engine,  twice  in  the  period  of  rotation.     It 

is  proper  to  consider  this  valve  as  a  pair  of  valves  operating 

on  one  port,  each  valve  closing  and  opening  the  port  in  turn  — 

this  being,   in    fact,   a  distinctive   feature  of   the  Gonzenbach 

cut-off. 

When  there  is  a  separate  passage  from  the  cut-off  valve  to 
each  cylinder-port,  steam  is  cut  off  by  one  of  the  port  edges 
only.  A  slide  of  the  simplest  description,  to  cut  off  at  one  end 
of  the  cylinder,  is  shown  in  Fig.  50.  It  is  shown  in  its  central 
position;  that  is,  when  the  eccentric  is  at  half-throw.  It  has 
lap,  and  will,  therefore,  cover  the  port  entirely  during  more  than 
half  the  period  of  rotation.  Fig.  5 1  represents  a  cut-off  valve 


82 


THE  SLIDE-VALVE   AND  ITS  FUNCTIONS. 


with  negative  lap.  It  will  cover  the  port  during  less  than  half 
the  period  of  rotation.  In  both  cases  steam  is  cut  off  by  edges 
A  and  B.  The  motion  of  these  two  valves  is  represented  by 
diagrams  52  and  53  respectively.  The  second  valve  has  only 


Fig.  50    >v; 


half  the  throw  of  the  first  one,  but  it  yields  as  large  a  port- 
opening  and  a  sharper  cut-off.  It  could  not  be  used  as  a  main 
admission-valve,  because  it  is  open  during  more  than  half  the 
period  of  rotation,  but  it  is  the  proper  construction  for  a  cut-off 
valve. 


Fig.  53 


Rg.52 


The  right-hand  side,  or  half,  of  the  valve  of  the  Gonzenbach 
cut-off  operates  as  represented  in  diagram  53,  but  the  left-hand 
side,  cutting  off  by  the  opposite  port-edge,  covers  the  port  part 
of  the  time  when  it  would  be  left  open  by  the  right-hand  side 
of  the  valve,  and  vice  versa.  The  motion  diagram  of  this  valve 
is  represented  in  Fig.  54.  Note  that  in  this  diagram  the  port- 


INDEPENDENT  CUT-OFF, 


83 


opening  is  shown  on  both  sides  of  the  center  line,  and  it  should 
be  measured  from  one  of  the  two  lap  lines  toward  the  center 
line.  The  point  of  cut-off  may  be  automatically  varied  by  rota- 
tion of  the  cut-off  eccentric  on 
the  shaft ;  but  in  that  case  the 
cut-off  is  limited  to  one-half  of 
the  piston  stroke,  for  the  valve 
must  be  capable  of  holding  the 
port  open  or  closed  in  the  same 
length  of  time,  the  limit  of 
which,  in  this  case,  is  one- 
fourth  of  the  period  of  rotation. 
This  valve  is  not  used  now,  for 
other  reasons  besides  its  limited 
range  of  cut-off.  The  steam  in 
the  lower  part  of  the  steam- 
chest  will  expand  with  the 
steam  in  the  cylinder,  and  under  light  loads  the  cut-off  will  be 
very  short,  and  under  these  conditions  the  speed  cannot  be 
properly  regulated  by  the  operation  of  the  cut-off  valve. 

The  cut-off  valve  sometimes  slides  on  an  anchor-plate  which 
bears  against  the  back  of  the  main  valve,  and  there  are  passages 
through  the  anchor-plate  and  the  main  valve  which  conduct  the 
steam  to  each  cylinder-port  separately.  The  main  objection  to 
this  arrangement  is  that  the  anchor-plate  is  unnecessary,  for  the 
cut-off  valve  may  as  well  slide  on  the  back  of  the  main  valve 
directly. 


Fig.  54- 


THE    CUT-OFF    VALVE    ON    BACK    OF    THE    MAIN    VALVE. 

Fundamental  Principles. 

In  order  to  fully  understand  the  working  of  a  cut-off  valve 
on  the  back  of  the  main  valve  certain  fundamental  principles 
should  be  well  understood.  First,  it  should  be  recognized  that 


84 


THE  SLIDE-VALVE   AND   ITS  FUNCTIONS. 


the  action  of  the  cut-off  valve  depends  entirely  on  its  motion 
relative  to  the  main  valve  ;  and  if  this  relative  motion  can  be 
represented  abstractry  in  a  simple  manner  any  reference  to  the 
motion  of  the  main  valve  will  be  useless. 

In  Fig.  55  B  is  the  center  of  the  main  eccentric,  and  E  is 
the  center  of  the  cut-off  eccentric,  ancV  these  centers  are  con- 
nected by  an  imaginary  straight  lin^y  The  two  points  B  and 
E  form  a  connected  system  of  points,  which  moves  around  the 
center  A,  and,  at  the  same  time,  the  system  revolves  about 

itself,  or  about  some  point  in  the 
system  ;  thus  :  point  B  describes  a 
circle  around  point  A,  and,  at  the 
same  time,  point  E  describes  a  circle 
around  point  B.  Four  positions  of 
points  B  and  E  are  shown  by  full 
lines,  and  dotted  lines  indicate  the 
positions  E  would  take  if  it  did  not 
revolve  about  B ;  in  which  case  the 
cut-off  valve  would  evidently  not  slide 
on  the  main  valve  at  all,  and  there 
would  be  no  cut-off  action.  This 
action,  therefore,  depends  on  the  ro- 
tation of  E  around  B,  and  is  not  in 
the  least  effected  by  motion  of  B 
Fig.  55-  J>  about  A ;  and  the  relative  motion 

of  the  cut-off  valve  will  be  as  if  it  worked  on  a  stationary  seat, 
and  was  driven  by  an  eccentric  of  eccentricity  equal  to  distance 
B  E."  ^The  upper  circle,  Fig.  55,  represents  the  path  of  this 
equivalent  ideal  cut-off  eccentric,  and  corresponding  and  coin- 
cident positions  of  the  eccentrics  in  both  figures  are  indicated 
by  the  notation.  Note  that  corresponding  positions  of  the  cut- 
off eccentric  arm,  from  B  as  a  center  of  rotation  in  both  figures, 
are  parallel.  When  the  equivalent  eccentric  is  at  mid-throw 
the  cut-off  valve  is  in  its  central  position  relative  to  the  main- 


INDEPENDENT  CUT-OFF. 


valve,  and  if  the  cut-off  edges  were  then  "line  and  line,"  the 
cut-off  action  would  evidently  be  the  quickest  possible ;  and  the 
fallacy  of  the  common  statement  that  the  quickness  of  the  cut- 
off   is   due   to   the    fact    that  • 
main-  and   cut-valve    move    in 
opposite    directions,     becomes 
evident,  for,  as  in  .the  present 
case,  the  cut-off  may  become 

quicker  if  the  main  valve  does  not  move  at  all.  The  superiority 
of  the  independent  cut-off  lies  in  the  facts  that  no  restriction  of 
the  main  port-opening  is  required,  and  that  the  cut-off  may 
occur  when  the  virtual,  or  equivalent,  cut-off  eccentric  is  near 
the  middle  of  its  throw. 

The  independent  cut-off  action,  as  compared  with  the  single- 
valve  action,  is  shown  approximately  in  Fig.  56,  where  the 
shaded  area  represents  the  port-opening  for  one-quarter  cut-off 
with  separate  cut-off  valve,  and  the  flat  arc  represents  the 
corresponding  single-valve  opening. 

THE    MEYER    CUT-OFF. 

Fig.  57  shows  the  Meyer  cut-off,  which  has  been  in  use  since 
1842.  Adjustable  slides  work  on  the  back  of  the  main  valve, 
and  are  driven  by  a  separate  fixed  eccentric.  The  slides  are 

shown  close  together, 
which  is  the  adjustment  for 
latest  cut-off.  A  and  Bare 
cut-off  edges,  and  the  dis- 
tance they  are  apart  con- 
stitutes negative  lap,  which 
is  called  "  space."  By 
turning  the  screw  the  slides  are  separated  and  the  space  is  di- 
minished, which  has  the  same  effect  as  increasing  the  lap  on  other 
valves  ;  that  is,  it  brings  about  an  earlier  cut-off.  The  stem  of 
the  screw  extends  through  the  back  of  the  steam-chest  ;  and  it 


Fig.  57- 


Ame-ican  Xaehi 

The  Meyer  Valve. 


86 


THE  Sf.IDE-VALVE   AND   ITS  FUNCTIONS. 


may  be  turned,  without  stopping  the  engine,  by  means  of  a 
hand-wheel  mounted  on  a  sleeve.  The  main  valve  has  an  ex- 
tension on  each  end,  which  contains  the  passage  through  which 
the  steam  is  conveyed  to  the  main  cylinder-port  ;  otherwise  the 
face  of  this  valve  is  constructed  as  that  of  a  common  slide- 
valve,  designed  to  cut-off  at  about  three-quarters  of  the  piston- 
stroke. 

THE    MEYER    CUT-OFF    DIAGRAM. 

The  essential  data  required  for  the  design  of  the  Meyer  cut- 
off mechanism,  can  readily  be  obtained  by  paying  close  attention 
to  fundamental  principles.  The  lower  circle,  Fig.  58,  repre- 
sents the  path  of  the  main  eccentric.  At  the  end  of  the  hori- 
zontal diameter,  and  with  radius  equal  to  the  lead,  make  a  small 


Adjust.  J 
rnent 


Fig.  58. 


American  Machinist 


circle,  as  shown,  and  draw  a  chord  touching  this  circle,  and 
whose  projection  on  the  diameter  of  the  eccentric-circle  bears 
the  same  proportion  to  the  whole  diameter  as  the  distance 
traversed  by  the  piston  before  steam  is  cut  off  by  the  main 
valve  bears  to  the  whole  stroke,  and  which,  in  the  present  case, 


INDEPENDENT  CUT-OFF.  8T 

is  supposed  to  be  as  three  to  four.  A  radius  at  right  angles  to 
this  chord  indicates  the  position  of  the  main  eccentric,  B,  when 
the  crank  is  at  its  dead  center  at  C.  With  a  radius  somewhat 
smaller  than  that  of  the  main  eccentric,  draw  a  circle  directly 
above,  as  shown.  This  circle  represents  the  path  of  the  equiva- 
lent or  ideal  cut-off  eccentric.  The  extreme  range  of  adjust- 
ment of  the  cut-off  valve,  relative  to  the  port  on  the  back  of  the 
main  valve,  is  indicated  to  the  left,  where  the  cut-off  valve  is 
shown  in  its  middle  position,  adjusted  for  earliest  and  latest  cut- 
off respectively. 

First  fix  the  cut-off  position  of  the  equivalent .  eccentric 
Avhen  the  valve  is  set  for  latest  cut-off.  P"or  reasons  which 
will  appear  afterwards,  this  position  should  be  near  the  ex- 
tremity of  the  throw ;  let  it  be  at  D  in  the  upper  circle. 
When  the  piston  has  traversed  three-quarters  of  its  stroke, 
the  equivalent  cut-off  eccentric  is  at  D,  at  the  instant  that  it 
closes  the  port ;  and,  therefore,  by  marking  off  from  D  back- 
wards the  three-quarter  stroke  angle  V,  the  point  K  is  located, 
which  marks  the  position  of  the  equivalent  eccentric  when 
the  crank  is  on  its  dead  center,  at  the  commencement  of  the 
stroke;  and  by  transferring  the  arm  BE  to  a  parallel  position 
on  the  main-eccentric-circle,  as  shown,  the  proper  location  of 
the  cut-off  eccentric  relative  to  the  crank-shaft  is  obtained. 
The  speed  of  the  engine  is,  in  the  present  case,  supposed  to 
be  regulated  by  a  throttling  governor,  and  the  point  of  cut-off 
will  only  be  varied  occasionally,  to  suit  the  load  or  steam-pres- 
sure ;  and  it  is,  therefore,  not  necessary  to  cut  off  the  steam 
earlier  than  at  one-quarter  of  the  stroke.  Make  angle  EF  equal 
to  the  quarter-stroke  crank-angle,  and  F  will  mark  the  one- 
quarter  cut-off  position  of  the  equivalent  eccentric,  and  the1 
distance  of  F  from  the  vertical  center-line  gives  the  negative  lap 
or  valve-space  for  earliest  cut-off,  while  the  valve-space  required 
for  latest  cut-off  is  given  by  the  horizontal  distance  of  point  D 
from  the  center  line ;  and  the  horizontal  distance  between  these 


88  THE   SLIDE-VALVE   AND   ITS  FUNCTIONS. 

two  points  represents  the  entire  range  of  adjustment  of  the  cut- 
off valve  in  the  present  case.  If  earlier  cut-off  is  required,  the 
valve-space  must  be  made  smaller.  For  cut-off  at  one-eighth  of 
the  stroke,  the  cut-off  edges  would  coincide,  and  for  still  shorter 
cut-off,  the  valve  would  overlap  the  port  in  its  midled  position. 
The  motion  is  quickest  at  the  middle  of  the  throw,  and  the 
quickest  cut-off  is  that  which  occurs  at  or  near  mid-throw,  of 
the  equivalent  eccentric.  The  radius  of  the  eccentric-circle 
may  represent  maximum  speed  of  relative  motion  at  mid-throw, 
and  at  other  points  it  is  represented  by  vertical  ordinates  to  the 
horizontal  diameter.  It  will  be  seen  that  sharper  cut-off  could 
be  had  for  the  entire  range  by  moving  point  D  farther  back  on 
the  circle  ;  but  this  would  also  throw  point  E  farther  back,  and 
would  increase  the  diameter  of  the  cut-off  eccentric ;  and  as  it 
so  happens  that  a  sharp  cut-off  earlier  in  the  stroke  is  of  more 
consequence  than  later  in  the  stroke,  the  arrangement  here 
shown  is  generally  adopted.  Thus  it  appears  that  the  design 
of  the  Meyer  valve-gear  is  restricted  by  a  desire  to  keep  down 
the  size  of  the  cut-off  eccentric  ;  and  it  will  also  be  readily 
seen  that  the  eccentrics  cannot  very  well  be  of  same  diameter, 
unless  the  range  of  cut-off  be  limited  to  five-eighths  of  the 
stroke.  The  latest  cut-off  may  occur  before  the  main  port  is 
closed,  and  in  that  case  the  short  period  during  which  the  cut- 
off valve  is  closed,  as  shown  on  the  diagram,  must  be  taken  into 
account ;  for  otherwise  it  may  happen  that  the  cut-off,  port  is 
open  again  before  the  main  port  is  closed.  The  location  of  the 
cut-off  eccentric,  when  the  main  port  is  closed,  is  found  by 
marking  off  the  corresponding  crank-angle  from  point  E  forward. 
It  will  probably  be  admitted  that  the  graphical  method  here 
shown  is  simpler  than  that  invented  by  Dr.  Zeuner ;  but  the 
greater  advantage  of  the  method  here  presented  lies  in  the  fact 
that  the  geometrical  construction  is  less  artificial,  and  may 
readily  be  reasoned  out,  and  may  therefore  be  retained  in  the 
mind  more  readily  than  any  process  that  must  be  learned 


INDEPENDENT  CUT-OFF,  89 

mechanically,  and  which  requires  a  somewhat  complex  geomet- 
rical construction  which  must  be  produced  before  the  problem 
is  considered.  For  the  sake  of  simplicity  and  clearness,  it 
seems  better  to  use  the  simple  Sweet  diagram  for  the  main 
valve,  and  treat  the  cut-off  valve  separately  ;  for  nothing  is 
gained,  and  much  may  be  lost,  by  drawing  so  many  lines  and 
circles  in  one  figure.  It  should  also  be  considered  that  the 
planning  of  the  valve  motion,  and  not  the  drawing  of  the 
diagrams,  takes  the  designer's  time.  It  does  not  pay  to  rub  out 
many  lines  and  draw  others  in  their  place  ;  for  paper  is  cheap, 
and  the  drawing  of  a  fresh  diagram  requires  but  little  time,  and 
this  time  is  of  little  consequence  if  the  valve-gear  to  be  desired 
is  worth  anything. 

LIMITATIONS    OF    THE    MEYER    CUT-OFF. 

The  Meyer  valve-gear  is  admirably  adapted  for  hand  adjust- 
ment, but  the  adjusting  screw  may  be  operated  by  the  governor. 
This  may  be  accomplished  by  means  of  a  rack  and  pinion,  but 
the  motion  required  and  the  friction  of  the  screw  are  unfavor- 
able conditions  for  a  satisfactory  regulation  of  the  speed  of  the 
engine ;  and  the  difficulty  is  increased  by  the  fact  that  if  the 
range  of  cut-off  is  to  extend  to  the  beginning  of  the  stroke, 
the  adjustment  of  the  slides  will  be  about  twice  that  required 
if  the  cut-off  is  beginning  at  one-quarter  of  the  stroke.  By 
making  the  right-hand  screw  and  left-hand  screw  of  different 
pitch,  the  cut-off  can  be  made  to  conform  closely  to  the  irregu- 
larity of  the  piston-motion  caused  by  the  angular  motion  of  the 
connecting  rod.* 

THE    RIDER    CUT-OFF    VALVE. 

If  the  cut-off  ports  on  the  back  of  the  main  valve  are  made 
converging,  and  the  cut-off  edges  of  the  valve  are  made  to  con- 
form to  this,  the  lap  or  valve-space  may  be  varied  by  a  lateral 

*  The  effect  of  the  angular  motion  of  the  connecting-rod  is  explained  in  the  last  chapter. 


90 


THE  SLIDE-VALVE   AND  ITS  FUNCTIONS. 


adjustment  of  the  cut-off  valve.  This  principle  holds  if  the 
valve  surface  is  made  cylindrical,  in  which  case  the  valve-seat 
becomes  concave,  and  the  cut-off  edges  become  right-  and  left- 
hand  screw-lines  of  steep  pitch.  The  adjustment  for  earlier  or 
later  cut-off  is  then  effected  by  a  partial  rotation  of  the  cut-off 
valve,  which  is  done  automatically  by  a  governor  of  the  Porter 
type,  by  means  of  a  rack  which  engages  a  pinion  on  the  valve- 
stem.  This  form  of  valve-gear  was  invented  by  A.  K.  Rider  of 
New  York,  and  it  has  been  applied  to  quite  a  number  of  en- 
gines ;  but  at  the  present  time  the  combination  of  a  shaft 
governor  and  a  single  balanced  valve  is  preferred. 

CUT-OFF    VARIED    BY    ROTATING    ECCENTRIC    ON    THE    SHAFT. 

The  cut-off  valve  may  be  a  simple  slide  with  inner  or  outer 
cut-off  edges,  driven  by  an  eccentric  loosely  journaled  on  the 
engine-shaft  and  connected  with  a  shaft  governor,  which  auto- 
matically changes  the  cut-off  in  relation  to  the  piston-stroke,  by 
rotating  the  eccentric  on  its  journal. 

Fig.   59    shows  a  main  valve  similar  to  that  in  the  Meyer 
system.     On  the  back  of  this  valve  is  a  slide,  which  cuts  off 


Fig-  59- 

the  steam  by  its  outer  edges.  Both  valves  are  shown  in  their 
central  position,  in  order  to  show  the  lap,  and  the  negative  lap, 
or  space,  of  the  cut-off  valve  will  be  noticed.  The  main  valve 
operates  as  a  common  slide  valve,  cutting  off  steam  at  about 
three-fourths  of  the  piston-stroke. 


INDEPENDENT  CUT-OFF. 


91 


Fig.  60  represents  the  relative  motion  of  a  cut-off  valve. 
B  may  represent  the  center  of  the  main  eccentric,  supposed 
stationary.  Let  the  relative  throw  of  the  cut-off  eccentric  be 
represented  by  the  smaller  circle,  then  the  point  of  cut-off  will 
be  at  D  ;  but  if  the  throw  is  increased,  as  shown  by  the  larger 
circle,  then  the  point  of 'cut-off  will  be  at  F.  E  and  F  mark 
different  positions  of  the  cut-bff  eccentric  at  the  beginning  of 
the  piston-stroke.  When  this  eccentric  is  in  position  E  it  will 
cut  off  steam  at  three-fourths  of  the  stroke,  and  in  the  position 
F  no  steam  will  be  admitted  to  the  cylinder.  For  intermediate 
cut-offs  the  eccentric  would  be  lo- 
cated somewhere  between  points  E 
and  F.  Angle  V  measures  1 20  de- 
grees ;  and  from  E  to  F  the  eccen- 
tric moves  through  an  angle  of  120 
degrees  minus  angle  U  or  nearly  90 
degrees.  It  will  be  seen  that  an 
increase  of  the  throw  diminishes  the 
angular  adjustment.  If,  therefore, 
the  cut-off  eccentric  be  so  located 
in  relation  to  the  main  eccentric  that 
when  it  is  rotated  on  the  engine- 
shaft  the  distance  between  the  eccentric  centers  is  increased 
while  the  cut-off  eccentric  is  angularly  advanced,  a  considerable 
range  of  cut-off  may  be  obtained. 

Diagram  61  shows  how  to  find  the  position  of  the  eccentrics, 
the  relative  motion  of  the  cut-off  eccentric,  the  lap  of  the  valves, 
etc.  The  lower  circle  represents  the  throw  of  the  main  eccen- 
tric, which  is  fixed  on  the  shaft,  and  the  dimensions  of  the 
main  valve  are  shown  by  Sweet's  parallel  lines,  which  also  deter- 
mine the  position  B  of  the  main  eccentric.  The  upper  circles 
represent  the  motion  of  the  cut-off  eccentric  around  the  center 
of  the  main  eccentric.  The  smaller  circle  represents  the  relative 
throw  of  the  cut-off  eccentric  for  latest  cut-off,  D  being  the 


9; 


THE   SLIDE-VALVE   AND   ITS  FUNCTIONS. 


-MAX-IMUM-RELA-T-IVE— T-tHRO 


point  of  cut-off.  Make  angle  D-E  120  degrees,  and  draw  B-E 
parallel  B-E  in  the  lower  figure.  This  fixes  the  location  of  the 
cut-off  eccentric  E.  Draw  large  upper  circle  to  make  shaded 
part  include  a  little  more  than  120  degrees  of  the  circle,  and 
make  B-F  parallel  B-F  in  the  lower  figure.  This  determines 
the  position  F  of  the  cut-off  eccentric  at  shortest  cut-off,  and 

E-F  is  the  angle  it  must  be 
rotated  on  the  engine-shaft. 
Note  that  radius  B-E  must 
be  a  little  more  than  the  neg- 
ative lap  in  order  to  keep  the 
cut-off  port  closed  a  short 
time  after  the  main  port  is 
closed.  Angle  V  represents 
the  range  of  cut-off,  which  in 
this  case  is  120  degrees  of 
crank  angle,  or  three-fourths 
of  the  stroke. 

This  construction  gives  a 
very  sharp  cut-off  early  in 
the  stroke,  and  a  large  port- 
opening.  The  latest  cut-off 
is  slow,  but  at  midstroke  it  is 
very  satisfactory.  The  cut- 
off eccentric  is  of  about  the 

Fie   61.  «/ 

same  size  as  the  main,  eccen- 
tric ;  but  its  relative  throw  for  short  cut-offs  'becomes  much 
greater.  The  cut-off  is  regulated  by  a  shaft  governor,  and  the 
greater  rate  of  adjustment  for  short  cut-offs  is  conducive  to 
close  regulation. 

The  rotative  movement  E-F,  in  the  lower  figure,  should 
not  be  greater  than  here  shown,  for  otherwise  it  will  be  very 
difficult  to  construct  connections  between  the  governor  weights 
and  the  eccentric,  which  will  be  durable  and  sufficiently  effec- 
tive in  the  extreme  positions. 


INDEPENDENT  CUT-OFF. 


93 


The  cut-off  valve  shown  in  Fig.  62  has  considerable  lap,  and 
it  cuts  off  by  inside  port  edges.  It  is  driven  by  an  eccentric 
journaled  on  the  engine-shaft,  and  controlled  by  a  shaft  gov- 
ernor, identically  in  the  manner  just  described. 


I 


// 

Fig.  62. 

The  valve  diagrams  are  shown  in  Fig.  63.  The  lower  circle 
represents  the  path  of  the  main  eccentric,  which  is  fast  on  the 
shaft,  and  also  the  circular  path  of  the  cut-off  eccentric,  both 
having  the  same  throw.  The  crank  is  at  its  dead  center,  at  C, 
the  main  eccentric  is  at  B,  and  the  cut-off  eccentric  is  at  E. 
This  is  the  natural  position  of  the  cut-off  eccentric  relative  to 
the  main  eccentric  when  the  engine  is  not  running,  or  before 
the  governor  begins  to  act,  and  when  steam  is  cut  off  a  little 
before  three-fourths  of  the  stroke.  When  the  proper  speed  is 
attained  the  governor  becomes  active,  and  turns  the  eccentric 
forward.  When  the  cut-off  eccentric  is  advanced  to  the  position 
F  steam  is  cut  off  right  at  the  beginning  of  the  stroke,  and 
intermediate  positions  of  the  cut-off  eccentric  cover  the  whole 
range  of  cut-off.  The  eccentricity  of  the  cut-off  eccentric  in 
regard  to  the  shaft  is  fixed,  but  in  regard  to  the  main  eccentric 
it  varies  between  the  two  extremes  represented  by  distances 
B-E  and  B-F.  The  upper  circles  represent  the  variable  throw 
of  the  cut-off  eccentric  in  relation  to  the  center  of  the  main 
eccentric,  B;  the  cut-off  action  being  as  if  the  valve-seat  were 
stationary  and  the  throw  of  the  eccentric  as  represented  by  the 
upper  circles.  F  marks  the  position  for  earliest  cut-off,  the 


94 


THE  SLIDE-VALVE   AND  ITS  FUNC1IONS. 


crank  being  on  its  dead  center,  as  shown  in  the  lower  figure. 
Make  B-F  parallel  B-F,  and  through  F  draw  a  vertical ;  this 
gives  the  lap  of  the  cut-off  valve.  With  radius  B-E  strike  a 
circle,  and  its  intersection  with  the  lap-line,  at  D,  marks  the 


COT -OP 


Fig.  63. 


latest  cut-off  relative  to  the  center  line  of  action,  which  is  sup- 
posed to  be  horizontal.  Draw  B-E  parallel  B-E,  and  angle  V 
is  equal  to  the  crank-angle  at  latest  cut-off,  that  is,  it  represents 
the  extreme  range  of  cut-off,  which  in  this  case  is  a  little  less 
than  three-fourths  of  the  stroke. 


INDEPENDENT  CUT-OFF.  95 

Point  E  marks  the  position  of  the  cut-off  eccentric  at  the 
commencement  of  the  stroke,  and  it  should  fall  outside  the  lap- 
line,  as  shown  ;  for  the  port  should  be  open  before  the  com- 
mencement of  the  stroke.  The  moment  the  eccentric  passes 
the  lap-line  steam  is  cut  off,  and  the  rapidity  of  valve-motion  at 
this  point  is  represented  by  the  distance  above  the  horizontal 
center  line.  At  the  beginning  of  the  piston-stroke  the  cut-off 
action  is  slow,  but  it  increases  rapidly.  K  marks  the  cut-off 
at  one-fourth  of  the  piston-stroke,  and  at  this  point  the  motion 
is  as  quick  as  that  of  the  Meyer  cut-off,  and  the  port-opening  is 
more  than  four  times  that  obtainable  with  a  single  valve.  For 
very  early  cut-off  the  port-opening  becomes  exceedingly  small, 
and  for  this  reason  a  valve  with  negative  lap  is  probably  pref- 
erable. The  small  port-opening  "wiredraws"  the  steam,  re- 
ducing the  initial  steam-pressure  in  the  cylinder,  and  therefore, 
at  very  early  cut-off  this  valve  would  not  admit  enough  steam  to 
run  the  engine  alone,  in  other  words,  there  would  be  no  early 
cut-off.  It  is  as  yet  unsettled  whether  this  would  be  detrimental 
or  beneficial  to  steam  economy.  At  any  rate,  it  will  only  be 
of  consequence  when  the  engine  is  underloaded. 

When  laying  out  the  valve-motion  the  following  must  be 
observed :  The  cut-off  valve  should  preferably  open  the  port  a 
little  before  commencement  of  the  stroke  ;  that  is, point  F  should 
be  a  little  above  point  B.  The  movement  around  the  shaft 
should  not  exceed  a  certain  limit,  for  otherwise  it  will  be  difficult 
to  construct  proper  governor  connections.  The  range  of  cut-off 
should  not  be  much  less  than  three-fourths  of  the  stroke.  It 
will  be  noticed  in  Fig.  62  that  the  tail-end  of  the  cut-off  valve 
opens  the  port  a  second  time,  which  in  no  case  must  happen 
before  the  main  port  is  closed.  To  guard  against  this  a  vertical 
line  is  drawn  in  the  upper  diagram,  to  the  right  from  the  center, 
at  a  distance  equal  to  the  tail-lap  of  the  valve,  and  the  intersec- 
tion of  this  line  with  the  eccentric-circles  shows  the  angle  turned 
by  the  crank  before  the  port  is  uncovered. 


'96  THE  SLIDE-VALVE   AND  ITS  FUNCTIOiYS. 

The  great  friction  of  the  common  D-valve  makes  it  unsuited 
for  single-valve  automatic  cut-off  engines,  but  in  combination 
with  a  cut-off  valve  it  operates  under  different  conditions.  The 
pressure  in  the  exhaust-cavity  is  but  little  more  than  that  of  the 
atmosphere,  while  the  corresponding  area  on  the  back  of 
the  valve  is  exposed  to  full  steam-pressure.  It  is,  therefore, 
desirable  to  reduce  the  exhaust-area  as  much  as  possible,  and  to 
shorten  the  travel.  In  single-valve  automatic  engines,  and  in 
locomotives,  the  small  port-opening  by  short  cut-off  must  be 
taken  into  consideration,  but  with  a  fixed  cut-off  at  three-fourths 
of  the  stroke  the  conditions  are  quite  different.  The  travel  can 
in  that  case  be  very  short ;  for  the  port  opens  quickly  at  the 
beginning  of  the  stroke,  and  it  is  not  necessary  that  it  uncover 
the  port  entirely.  The  shorter  travel  makes  it  feasible  to  reduce 
the  exhaust-cavity,  and  when  properly  proportioned  the  common 
D-valve  with  a  riding  cut-off  will  possess  some  points  of  merit 
not  claimed  for  the  balanced  valve. 

GRIDIRON    VALVES    WITH    INDEPENDENT    CUT-OFF. 

Flat  gridiron  valves  are  used  with  cut-off  valves  of  the  same 
description.  A  longitudinal  section  through  a  pair  of  such 
valves  is  shown  in  Fig.  64.  The  cut-off  valve  is  supposed  to 


_ 

Fig.  64.          \   t> 

be  in  its  central  position  in  relation  to  the  main  valve,  and  the 
space  between  the  bars  represents  negative  lap.  These  valves, 
cut-off  by  one  port-edge  only,  which  may  be  either  one  of  the 
two  edges.  They  are  used  in  four-valve  engines,  and  there  is 


INDEPENDENT  CUT-OFF,  91 

one  set  at  each  end  of  the  cylinder,  and  there  can  only  be  one 
cut-off  for  each  rotation  of  the  eccentric  ;  but  the  opposite  edge 
of  the  adjoining  bar  will  cover  the  port  part  of  the  time  while 
the  main  port  is  closed.  This  is  merely  incidental  to  this  par- 
ticular valve  construction;  for,  it  being  desirable  to  have  a  great 
number  of  ports,  the  bridges  are  made  just  wide  enough  to 
avoid  uncovering  the  port  a  second  time  in  one  stroke  of  the 
valve,  that  is,  moving  in  one  direction.  The  port  will  therefore 
not  remain  open  as  long  as  indicated  by  diagram  61,  but  there 
will  be  a  period  of  closed  port  on  the  right  hand  of  the  center 
of  the  upper  circles  corresponding  to  the  period  of  closed  port 
on  the  left  side.  The  second  closing  will  in  no  case  take  place 
before  the  main  valve  has  closed  the  cylinder-port ;  and  it  is 
rather  an  advantage  to  have  the  cut-off  port  closed  during  part 
of  the  exhaust  period,  for  it  may  prevent  leakage  into  the 
exhaust. 

If  the  cut-off  must  be  carried  as  far  as  three-fourths  of  the 
stroke,  and  there  is  a  rectilinear  transmission  from  the  eccentric 
to  the  valve,  then  the  width  of  the  bridges  should  be  about  two 
and  three-quarter  times  the  width  of  the  port.  There  are  three 
points  which  keep  the  design  of  these  valves  within  narrow  limits, 
viz.,  the  size  of  the  eccentric,  the  angular  adjustment  of  the 
eccentric,  and  the  parallelism  of  the  eccentric-rods.  If  the  cut- 
off is  not  to  be  later  than  at  five-eighths  of  the  stroke  more 
satisfactory  proportions  and  shorter  travel  may  be  had. 

BEGTRUP'S    ECCENTRIC. 

If  the  cut-off  eccentric  were  mounted  on  a  journal  concen- 
tric with  the  center  of  the  main  eccentric  its  relative  throw 
would  be  constant  and  short,  but  there  are  great  practical  diffi- 
culties in  the  way  of  this  scheme  when  applied  to  large 
engines.  It  would  make  a  very  large  eccentric  on  a  very 
large  journal,  and  the  friction  and  inertia  would  be  too  great 
for  a  sensitive  governor.  The  bearing,  movement  and  throw 


98 


THE  SLIDE-VALVE   AND  ITS  FUNCTIONS, 


of  the  cut-off  eccentric  may  be  reduced  in  a  practical  manner 
now  to  be  described. 

In  Fig.  65  B  is  the  center  of  the  main  eccentric,  and  E  and 
F  mark  the  positions  of  the  cut-off  eccentric  for  latest  and  ear- 
liest cut-off  respectively.  It  will  be  noticed  that  the  throw  is 

not  greatly  increased  in  the  early 
cut-off  position  if  the  eccentric 
is  movable  on  the  curved  track 
E-F.  It  could  be  made  so  by 
swinging  it  from  a  point  P ;  but 
this  point  would  be  inside  the 
engine-shaft,  and  cannot  be  used 
as  a  fulcrum.  Identically  the 
same  motion  may,  however,  be 
given  the  eccentric  by  suspend- 
ing it  from  two  short  links,  one 
on  each  side  of  the  shaft,  as 


Fig.  65. 


shown  in  Fig.  66.     To  bring  the 


eccentric  central  over  the  shaft, 
as  here  shown,  it  will  be  necessary  to  swing  it  around  the 
center  B  through  an  angle  of  35  degrees,  and  this  will  not 
alter  the  valve-motion  if  the  eccentric-rod  is  also  turned  35 
degrees  from  the  horizontal,  or  if  it  makes  that  angle  with  the 
main  eccentric-rod.  To  this  there  would  be  no  serious  objec- 
tion ;  for  the  rod  can  be  made  short,  and  an  angular  rocker 
would  transmit  the  motion  straight  to  the  valve.  In  its  central 
position  this  eccentric  becomes  concentric  with  the  shaft,  leaving 
the  valve  stationary.  The  cut-off  is  then  effected  by  the  motion 
of  the  main  valve  only.  The  relative  throw  is  considerably  less 
than  when  the  eccentric  is  moved  around  the  shaft,  and  this 
short  throw  makes  it  suitable  for  multiported  valves.  It  is  not 
necessary  that  the  cut-off  eccentric  be  swung  centrally  over  the 
shaft.  If  it  is  made  the  same  size  as  the  main  eccentric  the 
opening  for  the  shaft  may  be  to  one  side  from  the  center,  suffi- 


INDEPENDENT  CUT-OFF. 


99 


ciently  so  to  make  the  eccentric  rods  parallel,  and  this  does  not 
make  the  throw  in  relation  to  the  main  eccentric  any  greater. 
A  governor  of  the  simplest  description  may  be  used  with  this 
eccentric. 


Fig.  66.     Begtrup's  Eccentric. 

CUT-OFF    WITH    CONSTANT    TRAVEL    ON    MAIN    VALVE. 

The  cut-off  eccentric  may  be  journaled  concentric  with  the 
center  of  the  main  eccentric,  and  then  the  travel  of  the  cut-off 
valve  in  relation  to  the  main  valve  will  be  constant  ;  but  this 
arrangement  requires  an  enlargement  of  the  cut-off  eccentric, 
unless  the  cut-off  can  be  worked  from  the  end  of  the  engine- 
shaft. 

Fig.  67  shows  how  a  somewhat  radical  improvement  becomes 
possible  by  the  interposition  of  a  bell-crank  lever.  It  is  here 
shown  as  applied  to  a  vertical  engine,  but  it  is  also  applicable  to 
horizontal  engines.  The  crank  is  on  its  upper  dead  center,  at 
C,  and  the  main  eccentric  is  at  point  B,  which  is  also  the  center 
of  the  journal  of  the  cut-off  eccentric.  The  center  of  the  cut- 
off eccentric  is  at  E,  and  it  is  capable  of  rotative  adjustment 


100 


THE   SLIDE-VALVE   AND   ITS  FUNCTIONS. 


around  B  to  point  F.  When  at  this  point,  steam" is  cut  off  right 
at  the  commencement  of  the  stroke,  when  the  crank  is  on  its 
upper  dead  center,  as  shown  ;  and  the  latest  cut-off,  at  three- 
quarters  of  the  stroke,  is  obtained  when  the  eccentric  is  swung 
back  to  position  E.  The  valves  are  shown  in  Fig.  68  ;  they  are 


Fig.  67. 

placed  centrally  in  order  to  show  their  lap,  but  when  connected 
with  the  valve-gear  they  are  never  in  their  central  positions  at 
the  same  time.  The  cut-off  valve  is  actuated  by  a  bell-crank 
lever  which  effects  a  reversal  of  the  eccentric-motion,  and  so 
steam  is  cut  off  by  the  outer  edges  of  the  valve.  The  main 
valve  is  a  flat  plate  with  a  rectangular  exhaust  opening  in  the 


INDEPENDENT  CUT-OFF. 


101 


center  and  cut-off  ports  near  the  ends.  The  cut-off  valve  has  a 
pressure  balancing-ring  on  its  back,  which  relieves  the  main 
valve  of  the  greater  part  of  the  steam-pressure ;  and  as  the  com- 
pression is  constant  a  very  satisfactory  degree  of  balancing 
may  be  obtained  without  causing  the  valve  to  leave  its  seat 
under  any  circumstance,  except  when  forced  out  by  a  body  of 
water  in  the  cylinder.  The  travel  of  the  main  valve  is  constant, 
and  the  travel  of  the  cut-off  valve, 
in  relation  to  the  main  valve,  is  also 
constant.  The  travel  of  the  cut-off 
valve  in  relation  to  the  steam-chest 
cover  is  not  constant,  but  it  will  ap- 
pear from  an  inspection  of  Fig.  67 
that  the  maximum  throw  of  the  cut- 
off eccentric  is  less  than  the  throw 
of  the  main  eccentric.  Near  the 
middle  of  its  rotative  adjustment  its 
throw  is  greatly  reduced,  and  the 
valve  could  be  made  to  stand  still 
in  its  middle  position  if  the  radius 
of  the  curved  path  were  made  a 
little  longer.  It  is  noticeable  that 
the  shortest  valve  travel  occurs 
when  it  is  cutting  off  steam  at  one- 
fourth  or  three-eighths  of  the  stroke, 
under  which  condition  the  engine 
is  supposed  to  do  the  greater  part 
of  its  work.  Slide-valve  designs  involve,  to  a  great  extent,  the 
reconciliation  of  conflicting  requirements,  and  absoute  perfec- 
tion seems  unattainable  or  incompatible  with  great  simplicity ; 
but  the  combination  here  shown  has  many  good  points,  and  it 
would  often  be  serviceable. 

To  get  the  lap,  etc.,  of  the  cut-off  valve,  draw  a  circle  with 
radius  BF,  as  shown,  and  make  BF  parallel  BF.     Draw  a  center 


Fig.  68. 


102  THE   SLIDE-VALVE   AND   ITS  FUNCTIONS. 

line  parallel  FL,  and  at  right  angles  to  this  two  parallel  lines 
through  B  and  F  in  the  lower  circle :  the  distance  between 
these  is  negative  lap  or  valve-space,  which  added  to  the  radius 
gives  full  port-opening,  provided  both  arms  of  the  bell-crank 
lever  are  of  same  length.  The  diameter  of  the  smaller  circle 
represents  the  relative  motion  of  the  valves,  which  is  constant  ; 
and  the  smaller  part  of  the  circle,  cut  off  by  the  lap-line  through 
F,  represents  the  period  during  which  the  cut -off  port  is  closed, 
and  which  should  be  a  little  in  excess  of  the  period  during  which 
the  main  port  is  open  ;  it  should  in  this  case  encompass  more 
than  a  three-quarter  stroke  crank-angle.  As  the  throw  of  the 
equivalent  cut-off  eccentric  is  constant,  and  its  port -opening  is 
greater  than  its  half-throw,  it  follows  that  a  comparatively  short 
relative  motion  is  required,  to  give  as  much  opening  as  the  main 
valve  which  has  considerable  positive  lap.  An  unusually  large 
eccentric  is  therefore  not  needed,  but  it  must  need  be  somewhat 
larger  than  the  main  eccentric,  unless  the  diameter  of  the  shaft 
can  be  reduced.  The  main  eccentric-rod  is  supposed  to  be  ver- 
tical, and  it  is  necessary  that  the  eccentric-rods  form  an  angle 
between  them  as  shown,  in  order  to  get  the  desired  valve-motion. 

THE    BUCKEYE    VALVE-GEAR. 

Mr.  J.  W.  Thompson  has  designed  a  simple  and  ingenious 
valve-gear,  which  connects  the  motion  of  the  cut-off  valve  with 
that  of  the  main  valve  in  such  a  manner  that  the  travel  of  the 
cut-off  valve,  in  relation  to  the  main  valve  on  which  it  slides,  be- 
comes equal  to,  or  proportional  to,  the  throw  of  the  cut-off 
eccentric,  irrespective  of  its  position  relative  to  the  main  eccen- 
tric. The  cut-off  eccentric  may,  therefore,  be  journaled  directly 
on  the  engine-shaft ;  and  the  point  of  cut-off  may  be  changed  by 
a  rotative  adjustment  of  the  cut-off  eccentric  (regardless  of  the 
position  of  the  main  eccentric),  and  as  the  throw  of  the  cut-off 
eccentric  is  constant  the  relative  motion  of  the  cut-off  valve  will 
also  be  constant.  There  are  two  rocker-arms,  one  for  the  main 


INDEPENDENT  CUT-OFF. 


103 


eccentric  and  one  for  the  cut-off  eccentric.  The  cut-off  rocker 
is  carried  by  the  main  rocker,  and  it  is  fulcrumed  mid-way  be- 
tween the  valve  connection  and  the  fulcrum  of  the  main  roeker. 
It  is  a  counter-arm  rocker  of  same  total  length  as  the  main 
rocker  ;  and  the  lower  end,  to  which  the  eccentric-rod  is  pivoted, 
is  in  line  with  the  fulcrum  of  the  main  rocker  :  and,  this  being 
stationary,  it  follows  that  any  motion  transmitted  by  the  cut-off 
eccentric-rod  to  the  lower  end  of  the  cut-off  rocker  appears  re- 
versely relative  to  the  upper  end  of  the  main  rocker,  irrespective 
of  the  position  of  the  main  rocker  ;  that  is,  the  movement  of  the 
upper  end  of  the  cut-off  rocker  relative  to  the  main  rocker  is 
equal  to  the  throw  of  the  cut-off  eccentric  ;  and  as  both  valves 
receive  their  motion  from  the  upper  ends  of  the  rockers,  it  fol- 
lows that  the  travel  of  the  cut-off  valve,  relative  to  the  main 
valve  on  which  it  slides,  is  constant ;  and  that  steam  is  cut  off 
earlier  or  later  according  as  the  cut  off  eccentric  is  advanced  or 
moved  back  on  the  shaft. 

The  valve  used  on  the  Buckeye  engine,  in  connection  with 
the  compound  rocker  just  described,  is  shown  in  Fig.  69.     The 


Fig.  69.     The  Buckeye  Flat  Valve. 


body  of  the  main  valve  is  hollow,  and  two  narrow  cut-off  valves 
slide  on  inside  valve-faces,  next  to  the  cylinder  valve-faces.  The 
steam  enters  a  hollow  part  of  the  steam-chest  cover,  whence  it 
passes  through  sliding  ring-joints  to  the  inside  of  the  hollow 


104  THE   SLIDE-VALVE   AND   ITS  FUNCTIONS. 

valve,  and  from  there  through  the  cut-off  ports,  over  the  inside 
edges  of  the  main  ports,  to  the  cylinder.  The  exhaust  es- 
capes over  the  outside  port-edges  to  the  space  surrounding  the 
main  valve  and  which  connects  with  the  exhaust-pipe.  The 
main-valve  stem  is  hollow  and  the  cut-off  stem  passes  through 
it.  The  proportions  here  shown  are'  approximately  correct  for 
a  long-stroke  engine,  but  minor  details  are  not  shown.  This 
construction  has  the  advantage  of  short  and  direct  steam-pas- 
sages and  small  cylinder-clearance ;  and  as  the  unbalanced  pres- 
sure is  quite  moderate,  the  wear  of  the  valve-faces  cannot  be  of 
much  consequence,  and  at  the  same  time  this  pressure,  in  con- 
junction with  a  constant  travel,  insures  permanent  tightness  — 
unless  the  faces  are  cut  by  solid  matter  carried  over  by  the  steam. 
As  the  hot  steam  inside  the  main  valve  is  surrounded  by  exhaust- 
steam,  some  heat  may  be  lost  by  r evaporation  of  moisture  con- 
tained in  the  exhaust-steam ;  but  it  is  noteworthy  that  the 
builders  have  not  found  it  necessary  to  make  any  change  in  this 
respect  since  the  introduction  of  the  valve,  some  twenty-five 
years  ago. 


Fig.  70. 

Fig.  70  shows  the  principles  of  construction  of  the  valve- 
gear.  The  center  of  the  engine-shaft  is  at  A,  and  the  crank 
is  on  its  dead  center,  at  C.  The  main  eccentric  is  at  B,  and 
the  cut-off  eccentric  is  at  E,  and  the  compound-rocker  is  repre- 
sented by  two  crossed  lines.  The  lap  of  the  main  valve,  its 
point  of  cut-off,  etc.,  can  easily  be  determined  by  Sweet's  valve- 


JNDEPEiVDENT  CUT-OFF.  105 

diagram,  remembering  that  the  location  of  the  eccentric  must 
be  diametrically  opposite  that  obtained  from  the  diagram,  on 
account  of  the  inward  position  of  the  steam-edges.  The  path 
of  the  cut-off  eccentric  is  represented  by  a  separate  circle. 
Through  the  center  of  this  circle  draw  a  line  parallel  to  AL  ; 
and  at  right  angles  to  this,  in  a  distance  equal  to  half  the  width 
of  the  cut-off  port,  draw  a  chord,  as  shown.  The  distance  from 
the  center  represents  negative  lap,  and  point  F  marks  the 
position  of  the  cut-off  eccentric  for  earliest  cut-off.  The 
smaller  arc,  cut  off  by  the  chord,  represents  the  period  during 
which  the  cut-off  port  is  closed ;  and  it  is  only  necessary  to 
observe  that  this  port  must  not  open  before  the  main  port  is 
closed.  If,  for  instance,  the  main  port  is  closed  at  three- 
quarters  of  the  piston-stroke,  the  cut-off  valve  may  close  the 
cut-off  port  a  little  before  the  commencement  of  the  stroke, 
and  keep  it  closed  till  after  three-quarters  of  the  stroke  is 
traversed ;  and  no  steam  will  in  that  case  be  allowed  to  enter 
the  cylinder. 

If  great  accuracy  is  required,  the  varying  angularity  of  the 
eccentric-rod  may  be  taken  into  account ;  and  the  negative  lap 
or  valve-space  is  determined  accurately  by  drawing  the  lap-line 
through  F  at  right  angles  to  FL  above,  which  increases  the 
valve-space  slightly  ;  but  the  first  construction  is  satisfactory, 
for  its  error  is  small  and  on  the  safe  side. 

PISTON-VALVES    WITH    INDEPENDENT    CUT-OFF. 

Piston-valves  of  the  larger  sizqs  must  fit  loosely  in  the  valve- 
cylinder,  for  otherwise  they  will  occasionally  become  very  tight. 
They  are,  therefore,  provided  with  elastic  packing-rings  similar 
to  those  used  on  the  main  piston,  and  these  rings  will  cause 
some  wear,  and  if  the  travel  is  variable,  uneven  wear  may  be 
expected  ;  and  for  this  reason  it  is  claimed  that  piston-valves 
with  constant  travel  wear  better  than  those  that  regulate  the 
steam  admission  by  varying  their  travel  ;  and  as  a  relatively 


106 


THE   SLIDE-VALVE  AND   ITS  FUNCTIOArS. 


constant  travel  is  obtainable  with  the  independent  cut-off  gear, 
such  gear  may  profitably  be  used  in  connection  with  piston- 
valves  ;  and  as  these  valves  are  in  perfect  equilibrium  under 
any  steam-pressure,  they  may  have  a  long  travel  without  exces- 
sive wear  and  without  any  detrimental  effect  on  the  governor ; 
and  the  increased  travel  may  obviate  the  necessity  of  multiple 
ports,  which  in  any  event  is  of  questionable  utility  ;  for  it  in- 
creases the  chances  for  leakage. 

Fig.  71  shows  part  of  a  piston-valve  combination,  adopted  by 
the  Buckeye  Engine  Company.  The  cut-off  valve  is  inside 
the  main  valve,  and  the  arrangement  of  steam  and  cut-off  ports 
is  the  same  as  that  of  the  flat-faced  valves,  Fig.  69 ;  but  the 
travel  is  longer,  and  the  exhaust  steam  is  discharged  at  the 


Fig.  71.     The  Buckeye  Round  Valve. 


ends,  and  does  not  come  in  contact  with  the  hot  surface  of 
the  main  valve,  except  at  the  ends.  The  packing-rings  are  in 
the  best  possible  positions  to  prevent  leakage  ;  and  both  the 
main  and  cut-off  ports  are  bridged  in  a  number  of  places  to 
afford  ample  bearing  for  the  rings  when  they  pass  over  the  ports. 

CUT-OFF    VALVE    WORKED    BY    MEANS    OF    A    LINK. 

The  cut-off  valve  may  be  worked  by  a  rocking-link  as  indi- 
cated in  Fig.  72.     In  that  case  the  cut-off  eccentric  E  is  fixed 


INDEPENDENT  CUT-OFF. 


107 


on  the  shaft,  and  the  travel  of  the  cut-off  valve  is  varied  by 
moving  a  block  up  and  down  in  the  slotted  link  ;  which  may  be 
done  automatically  by  connecting  it  with  a  governor  of  the 


Fig.  72. 

vertical  type.  By  shifting  the  link-block  the  throw  is  increased 
or  diminished,  precisely  as  if  the  eccentric  were  shifted  on  a 
radial  line  from  the  center  of  the  shaft.  In  Fig.  73,  lower 
circle,  the  main  eccentric  NEG.  L/cp 

is  at  B,  and  the  cut-off  ec- 
centric is  at  E,  and  the 
crank  is  at  its  dead  center, 
at  C.  When  the  link-block 
is  in  its  lowest  position,  the 
valve-motion  is  as  if  the  ec- 
centric were  at  F  and  its 
horizontal  motion  were  com- 
miuiicated  straight  to  the 
valve  ;  and  shifting  the  link- 
block  to  its  upper  position 
corresponds  to  a  radial  dis- 
placement of  the  eccentric 
to  point  E' ;  and  in  this  po- 
sition BE'  is  the  radius  of 
the  equivalent  cut-off  ec- 
centric, as  if  actuating  the 
valve  on  a  stationary  valve- 
seat.  With  radius  BF 

strike  a  circle,  as  shown  above,  and  make  BF  parallel  BF. 
Through  F  draw  a  line  at  right  angles  to  AL,  Fig.  72  ;  its 


108  THE   SLIDE-VALVE   AND   ITS  FUNCTIONS. 

distance  from  the  center  determines  the  negative  lap  required. 
With  radius  BE'  draw  a  circle  and  make  BE'  parallel  BE'  ;  the 
angle  V  determines  the  range  of  cut-off.  As  the  ideal  eccen- 
tric is  supposed  to  move  radially,  its  throw  in  regard  to  its 
virtual  center  of  revolution  at  B  must  vary  considerably ;  and  it 
is  observable  that  it  is  least  near  the  middle  of  its  radial  path 
when  steam  is  cut  off  at  about'  one-quarter  of  the  piston-stroke  ; 
but  considering  that  the  valve  has  negative  lap,  and  cuts  off 
near  its  mid-stroke,  the  valve-action  would  be  satisfactory  at 
moderate  piston-speed.  The  cut-off  valve  may  be  a  plain  flat 
slide,  cutting  off  steam  by  its  outer  edges  ;  and  it  can  be  con- 
structed with  two  cut-off  edges  at  each  end  to  operate  on 
double-ports,  though  a  constant  relative  travel  is  much  better 
for  double-ported  valves. 

As.  here  shown  the  maximum  cut-off  will  be  at  3-4ths  of  the 
stroke.  Much  more  satisfactory  valve  proportions  can  be  had 
if  the  cut-off  is  limited  to  5-8ths  of  the  stroke. 

INDEPENDENT    CUT-OFF    ON    FOUR-VALVE    ENGINES. 

TJie  Mclntosh  &  Seymour  Valves. 

Fig.  74  represents  a  sectional  view  of  the  Mclntosh  &  Sey- 
mour valves  and  valve-gear.  There  are  two  main  valves  at 
each  end  of  the  cylinder,  one  for  admission  and  one  for  ex- 
haust. It  is  plain  flat  gridiron  valves,  on  detachable  seats, 
and  they  move  transversely  to  the  cylinder. 

In  the  valve-gear,  links,  which  are  used  to  transmit  motion 
to  the  valves,  are  actuated  by  swinging  rockers  in  such  a  way  as 
to  distort  the  motion  as  received  from  the  eccentric,  hastening 
the  movement  of  the  valve  when  near  one  end  of  its  stroke,  and 
at  the  other  end  causing  a  pause  in  its  motion,  so  that  while  a 
a  rapid  opening  and  closing  of  the  port  is  secured,  the  valve  re- 
mains practically  still  while  closed.  This  feature  and  the  large 
number  of  ports  in  the  valve  reduce  the  stroke  necessary  to  give 


INDEPENDENT  CU7-OFF. 


109 


full  port  opening  to  from  one-half  inch  up  to  one  and  one-half  inch 
for  cylinders  of  the  largest  size  ;  and,  since  the  movement  of  the 
valve  takes  place  chiefly  when  it  is  open  and  relieved  of  the 
pressure  of  the  steam,  the  wear  and  also  the  power  required  to 


Fig.  74.     Mclntosh  &  Seymour. 

operate  the  valve  is  reduced  to  a  small  amount.  And  since  the 
bars  or  bridges  between  ports  are  of  same  width  on  valve  and 
valve-seat,  the  wear  should  be  absolutely  even  on  the  entire  sur- 
face. 

On  the  top  of  the  main  steam-valve  is  a  cut-off  valve,  oper- 
ated by  a  movable  eccentric,  controlled  by  a  shaft  governor. 
The  eccentric  is  journaled  on  the  engine-shaft,  and  the  cut-off 
is  varied  by  varying  the  angular  position  of  the  eccentric  in  re- 
lation to  the  crank.  The  main  valves  are  driven  by  a  fixed  ec- 
centric, controlling  the  admission  of  the  steam  and  the  opening 


110 


THE  SLIDE-VALVE   AND   ITS  FUNCTIONS. 


and  closing  of  the  exhaust.  The  valve-gear  is  simply  an  arrange- 
ment of  links,  rock  shafts,  and  slides  for  transmitting  the  motion 
of  the  eccentrics  to  the  valves.  On  multi-cylinder  engines  the 
governor  usually  controls  the  cut-off  on  all  the  cylinders. 

Valves  of  the  Russell  Engine. 

Fig.  75  shows  the  valves  of  the  Russell  four-valve  engine. 
There  are  two  admission-valves,  one  at  each  end  of  the  steam- 
chest,  and  on  the  back  of  these  are  multiported  cut-off  valves. 
There  are  two  exhaust-valves  of  the  semi-rotary  kind  placed  un- 
derneath the  cylinder,  one  at  each  end.  Steam-  and  exhaust- 


Fig.  75.    The  Russell  Valves. 

valves  are  driven  by  one  eccentric,  which  is  fixed  on  the  shaft ; 
and  the  cut-off  valves  are  driven  by  an  eccentric  journaled  on 
the  shaft  and  connected  with  a  shaft  governor,  which  regulates 
the  cut-off  by  turning  the  eccentric  forward  or  backward  on  the 
shaft.  Fig.  76  shows  one  of  the  exhaust-valves.  It  is  triple 
ported  and  of  small  diameter.  As  the  valve-face  is  at  the  bot- 


INDEPENDENT   CUT-OFF. 


Ill 


torn,  it  will  not  become  leaky  when  worn.  These  valves  are  ac- 
tuated by  means  of  a  wrist-plate  of  the  Corliss  type,  which,  in 
conjunction  with  the  multiplication  of  ports,  makes  large  diame- 
ters unnecessary,  and  the  valve  cavity,  or  clearance,  is  thereby 
greatly  reduced. 

The  plates  and  springs  on  the  back  of  the  cut-off  valves,  Fig. 
75,  are  there  to  prevent  the  valves  from  leaving  their  seats  when 
the  steam-pressure  in  the 
steam-chest  is  reduced  be- 
low that  of  the  compressed 
steam  in  the  cylinder.  The 
compression  of  the  springs 
may  be  increased  by  means 


of  screws  from  the  outside 
of  the  chest-cover.  In  this 
connection  it  should  be 
noted  that  the  point  of  ex- 
haust closure  is  fixed,  and 
that  the  compression  cor- 
responds to  that  which  can 
be  had  at  latest  cut-off  in  a  single-valve  engine. 


Fig.  76.     The  Russell  Exhaust  Valve. 


It  will,  there- 
fore, never  become  excessive,  but  it  answers  its  purpose  when 
the  cylinder  clearance  is  sufficiently  small.  The  valves  will  only 
slam  when  the  throttle  valve  is  closed,  or  when  used  on  the  low- 
pressure  cylinder  of  a  non-condensing  compound  engine. 

The  Buckeye  Vibrating  Cut-off. 

Figs.  77  and  78  represent  sectional  front  and  end  elevations 
of  a  valve-gear  for  large  low-pressure  cylinders,  lately  brought 
out  by  the  Buckeye  Engine  Company.  There  are  four  main 
valves,  two  at  each  end  of  the  cylinder,  one  for  exhaust  and  one 
for  steam.  These  valves  are  of  the  Gridiron  pattern,  and  they 
move  in  a  direction  transversely  to  the  cylinder.  The  steam- 
valve  has  a  hollow  cylindrical  shell  cast  on  top  of  it,  and  bored 


112 


THE   SLIDE-VALrE   AND   ITS  FUNCTIONS. 


out  for  a  pair  of  cut-off  valves.  These  valves  extend  the  whole 
length  of  the  main  valve,  and  they  receive  rotative  reciprocal  mo- 
tion from  a  central  valve-shaft.  Steam  is  admitted  through 
openings  in  the  top  of  the  cylindrical  shell,  and  passes  through 


Fig.  77.     The  Buckeye  Vibrating  Cut-off. 


the  long  cut-off  ports  to  the  ports  of  the  main  valve.  The  mo- 
tion of  the  cut-off  valves  is  similar  to  that  of  the  Corliss  exhaust- 
valves.  These  valves  are  moved  by  an  eccentric,  journaled  on 
the  engine-shaft  and  connected  with  a  shaft  governor,  which 
regulates  the  cut-off,  in  relation  to  the  piston-stroke,  by  rotating 


INDEPENDENT  CUT-OFF. 


113 


the  eccentric  on  the  shaft.  The  stroke  of  the  valves  is  constant, 
and  earlier  or  later  cut-off  is  effected  by  turning  the  eccentric 
ahead  or  back  on  the  shaft.  The  main  valve  has  a  short  longi- 
tudinal motion,  derived  from  a  fixed  eccentric.  It  determines 
the  point  of  admission  and  gives  a  constant  lead. 


Fig.  78.  Buckeye  Valves. 
The  exhaust-valve  has  an  invariable  motion  similar  to  that  of 
the  steam- valve,  and  both  valves  are  driven  conjunctively  by 
means  of  a  vertical  rocker  shaft  with  short  arms,  which,  when 
placed  in  their  proper  relative  positions,  will  produce  the  toggle 
motion,  by  which  the  valve  motion  is  retarded  when  the  ports 
are  cfosed  and  accelerated  during  the  opening  period. 


114  7HL  SLIDE-VALVE  AND  2.^  FUNCTIONS. 

The  cuts  representing  this  valve-^  ,ar  were  reduced  from 
working  drawings ;  and  the  levers  and  valves  are,  for  obvious 
reasons,  not  shown  in  the  relative  positions  they  occupy  when 
in  operation. 

The  cylinder  here  shown  is  the  low-pressure  cylinder  of  a 
tandem  compound  engine.  The  high-pressure  cylinder  has  a 
valve  of  the  Buckeye  standard  round-valve  construction,  Fig.  71. 
The  riding  cut-off  in  this  construction,  as  well  as  the  vibrating 
cut-off  inside  the  gridiron  valves,  are  varied  by  angular  advance 
of  the  cut-off  eccentric,  enabling  both  systems  to  be  coupled  to 
the  same  eccentric  and  governor. 


THE  SLIDE-VALVE    ON  PUMPS.  115 


CHAPTER   V. 

THE    SLIDE-VALVE    ON    PUMPS. 

THE  common  D-valve  is  used  on  the  steam-cylinder  of  direct- 
acting  pumps.  In  these  pumps  steam  and  water  pistons,  or 
plungers,  are  on  a  common  piston-rod,  and  the  steam  and  water 
ends  are  connected  by  a  frame  or  bars.  There  are  two  distinct 
types  of  direct-acting  pumps,  Single  Pumps  and  Duplex  Pumps. 
They  are  all  double-acting ;  that  is,  steam  is  admitted  to  each 
side  of  the  piston  alternatingly.  The  Single  style  has  one 
steam-cylinder  and  one  water-cylinder.  The  Duplex  consists 
of  a  pair  of  single  pumps  of  same  size,  placed  side  by  side,  and 
the  peculiarity  of  this  type  is  that  the  motion  of  each  steam- 
valve  is  derived  from  the  piston  of  the  other  pump.  By  this 
arrangement  the  valve-moving  mechanism  becomes  simple  and 
its  action  positive,  and  these  are  the  main  reasons  why  the 
duplex  type  has  become  so  popular.  The  more  uniform  motion 
of  the  water  is  also  in  its  favor. 

The  slide-valve  moves  across  the  steam-ports,  alternatingly 
covering  and  uncovering  each  of  them  ;  and  there  is,  necessarily, 
a  central  position  where  both  ports  are  covered  (or  partly  un- 
covered). If  the  valve  stays  in  that  position  for  a  moment,  the 
pump  will  stop  ;  and  if  the  valve  stops  near  this  position,  leaving 
only  a  small  port-opening,  the  speed  will  be  more  or  less  re- 
tarded. Now  this  is  what  would  happen  if  the  valve-motion 
were  derived  directly  from  the  piston  of  the  same  pump.  The 
valve  would  slowly  cover  the  steam-port,  and  finally  bring  the 
,  pump  to  a  dead  stop,  before  the  end  of  its  stroke. 

The  means  adopted  to  overcome  this  difficulty  in  a  single 
pump  consists  chiefly  in  an  auxiliary  piston,  located  in  the 


116  THE  SLIDE-VALVE   AXD   ITS  FUNCTIONS. 

steam-chest  and  called  the  chest-piston.  This  piston  engages 
projections  on  back  of  the  main  valve,  so  that  valve  and  piston 
move  in  unison.  Before  the  end  of  the  stroke  of  the  main 
piston,  steam  is  admitted  to  one  end  of  the  chest-piston  and  ex- 
hausted from  the  other  end  ;  and  this  piston  is  consequently 
forced  over  to  the  exhaust-end,  carrying  the  slide-valve  with  it. 

The  steam -passages  leading  to  the  chest-piston  are  very 
small ;  when  they  are  uncovered  the  chest-piston  begins  to 
move,  and  after  that  the  valve-motion  is  independent  of  the 
motion  of  the  main  piston,  and  the  valve,  impelled  by  the  chest- 
piston,  will  now  entirely  uncover  the  steam-port  for  the  return 
stroke  of  the  pump. 

It  will  be  noticed  that  the  throttling  effect  of  .the  small 
auxiliary  steam-passages  is  of  importance,  for  the  short  period 
intervening  between  the  uncovering  of  the  small  auxiliary  ports 
and  the  starting  of  the  valve  is  essential  to  a  successful  opera- 
tion of  this  mechanism.  The  main  objection  is,  that  if  any  of 
the  small  passages  are  stopped  up  the  chest-piston  becomes- 
inoperative. 

The  inventor  of  the  direct-acting  steam-pump,  Henry  R. 
Worthington,  found  that  the  momentum  of  the  moving  parts  of 
the  engine  was  often  insufficient  for  the  purpose  of  throwing 
the  valve  clear  across  the  ports,  and  to  accomplish  this  he  de- 
vised a  combination  of  a  steam-valve  and  spring.  The  spring 
being  compressed  by  the  action  of  the  engine  while  the  valve 
remained  at  rest,  until  at  the  proper  time,  by  the  further  action 
of  the  engine,  the  spring  was  released  and  acted  upon  the  valve 
independently  of  the  momentum  of  the  engine.  This  device 
was  patented  in  1841.  Several  years  later  he  used  the  auxiliary 
piston. 

The  piston  speed  of  pumps  is  much  slower  than  that  of  a 
slow  running  steam-engine,  and  the  steam-ports  are  made  cor- 
respondingly small.  No  lap  is  required  on  the  valve,  and  this 
helps  to  reduce  its  travel  and  size.  The  steam-pressure  ordi- 


THE   SLIDE-VALVE    ON  PUM2*S. 


117 


narily  sustained  by  these  valves  is,  therefore,  of  no  consequence, 
and  the  common  D-form  is  eminently  suitable  for  pumps. 


THE    BLAKE    SINGLE    PUMP. 


The  valve-gear  of  the  Blake  Single  Pump  is  illustrated  in 
Figs,  i  to  4  below.  This  is  the  arrangement  of  the  boiler-feed 
and  pressure  pumps.  The  main  valve,  which  controls  the 
admission  and  exhaust  of  steam  from  the  main  cylinder,  is  car- 


COMBINED  MOVABLE  SEAT 
AND  AUXILIARY  VALVE 


XHAU8T  SIDft 


SECTIONAL  VIEW 

OF 

STEAM  END 


118  THE   SLIDE-VALVE   AND   ITS  FUNCTIONS. 

ried  by  the  chest-piston,  and  moves  on  the  back,  of  a  movable 
seat.  This  movable  seat  is  shown,  bottom  up,  in  Fig.  4.  The 
passages  A,  B,  C  serve  as  steam-ports  to  the  main  cylinder. 
The  lugs  G,  G'  control  the  admission  of  steam  to  the  chest- 
cylinder,  and  the  holes  H,  H'  control  the  exhaust  from  that 
cylinder. 

With  the  valve  in  the  position  shown,  the  course  of  the 
steam  is  through  live-steam-passage  N,  through  the  port  C  to 
the  right-hand  end  of  the  main  cylinder,  thus  forcing  the  piston 
over  to  the  left.  Now,  when  the  piston  nearly  reaches  the  left 
end  of  the  cylinder  the  movable  seat,  by  means  described  later,  is 
shifted  over  to  the  left,  so  that  the  lug  G  covers  the  port  E, 
while  the  lug  G'  moves  off  from  the  port  E',  thus  admitting 
steam  behind  the  chest-piston  at  the  left-hand  side.  At  the 
same  time  the  hole  H  in  the  movable  seat  places  K  and  S  in 
communication,  thus  exhausting  the  steam  from  the  right  side 
of  the  chest-piston.  This  piston  is  then  forced  over  to  the 
right,  and  the  port  A  is  uncovered  to  live  steam.  When  the 
piston  is  near  the  right-hand  end  of  its  stroke  all  the  operations 
are  repeated  in  the  opposite  direction. 

There  is  one  steam  and  one  exhaust  hole  at  each  end  of  the 
chest -cylinder  ;  and  the  movable  valve  seat  is,  in  effect,  an  aux- 
iliary valve,  which  controls  the  admission  and  exhaust  through 
said  holes.  The  chest-piston  passes  over  the  exhaust-hole  near 
the  end  of  its  stroke,  and  is  thus  cushioned  on  the  imprisoned 
steam.  The  valve  has  no  lap,  a  short  travel,  and  opens  simul- 
taneously for  steam  and  exhaust.  It  remains  open  till' the  piston 
stroke  is  nearly  completed,  when  it  is  suddenly  moved  to  the 
other  extremity  of  its  travel. 

It  will  be  seen  that  if  means  are  provided  to  shift  the  mov- 
able seat,  the  rest  of  the  operation  is  automatic.  To  accom- 
plish this  the  piston-rod  is  provided  with  a  cross-head,  on  which 
is  a  pin,  which  engages  a  lever  fulcrumed  at  P.  A  short  link 
connects  this  lever  with  a  tappet  on  a  sleeve,  which  slides  freely 


.      THE   SLIDE-VALVE    ON  PUMPS.  119 

on  the  valve-stem.  Near  the  end  of  the  stroke  the  tappet 
strikes  one  of  the  two  collars  on  the  stem  and  moves  the  valve- 
seat.  By  changing  the  position  of  these  collars  any  desired 
amount  of  lead  may  be  given  to  the  valve.  They  should  be  set 
so  as  to  admit  steam  in  time  to  stop  the  piston  before  it  strikes 
the  cylinder  head.  If  it  is  stopped  too  soon  the  steam  required 
to  fill  the  clearance  space  is  wasted. 

DEAN    BROTHERS. 

Dean  Bros'  Single-Pump  is  shown  on  page  120.  The  small 
slide,  shown  in  enlarged  horizontal  section  in  Fig.  6,  controls 
the  admission  and  exhaust  of  steam  to  and  from  the  chest-piston. 
Sunk  in  the  face  of  this  slide  are  diagonal  exhaust  cavities  d 
and  d'.  In  the  extreme  positions  of  the  slide  these  cavities 
connect  one  of  the  ports  b,  b'  with  the  exhaust  port  c,  while  the 
other  port  is  left  uncovered,  as  shown.  The  steam  is  admitted 
to  one  end  of  the  chest-piston,  and  exhausted  from  the  other 
end,  forcing  the  piston  over  to  one  end  of  its  cylinder ;  and 
when  the  slide  is  moved  to  the  other  extremity  of  its  travel 
this  operation  is  reversed.  The  chest-piston  carries  the  main 
slide-valve  by  means  of  a  lug  on  its  back  ;  and  thus  the  main 
-steam-ports  are  alternately  opened  to  steam  and  exhaust,  and 
with  the  stroke  of  the  auxiliary  slide  properly  regulated,  steam 
will  be  admitted  to  the  main  cylinder  in  time  to  stop  the  piston 
at  the  end  of  each  stroke. 

As  will  appear  from  the  illustration,  the  auxiliary  slide  re- 
ceives its  motion  from  a  rocker,  fulcrumed  in  the  latitude  of  the 
valve-stem.  It  is  a  continuous  motion  ;  and  the  ports  leading 
to  the  chest-piston  are  therefore  closed,  except  at  the  moment 
the  main  piston  is  being  reversed.  Hence  there  can  be  no 
"blow  through,"  or  waste  of  steam,  in  case  the  chest -piston 
becomes  worn.  The  stroke  of  the  pump  is  regulated  by  length- 
ening or  shortening  the  travel  of  the  auxiliary  slide,  which  is 
effected  by  shifting  the  stud  in  the  slot  in  the  upper  end  of  the 
rocker. 


"120  THE  SLIDE-VALVE   AND   ITS   FUNCTIONS. 


Dean  Bros'  Valve  Gear. 


THE   SLIDE-VALVE    ON  PUMPS,  121 


KNOWLES. 

In  the  Knowles  Pump  there  is  no  auxiliary  slide-valve ;  but 
when  the  main  piston  has  almost  completed  its  stroke  the  chest- 
piston  is  slightly  rotated,  whereby  small  ports  in  the  underside 
of  this  piston  -are  put  in  communication  with  corresponding 
ports  in  the  chest-cylinder,  and  thus  steam  is  admitted  to  one 
end  of  this  cylinder,  and  exhausted  from  the  other  end  through 
small  passages  in  the  piston.  The  rest  of  the  valve-motion  is 
practically  the  same  as  that  of  the  Blake  pump,  above  described. 
The  main  piston-rod  carries  an  arm  which  strikes  a  collar  on  the 
chest-piston  rod,  and  moves  the  chest-piston  if  it  should  fail  to 
start  at  the  proper  moment. 

THE    DAVIDSON    PUMP    GEAR. 

The  valve-gear  consists  of  a  valve,  valve-pistons,  valve-pin, 
and  cam.  The  valve  is  actuated  by  a  positive  mechanical  con- 
nection with  the  main  piston-rod,  and  by  the  action  of  steam  on 
valve-pistons.  Fig.  79  shows  the  valve-gear  and  steam-cylinder 
in  detail.  The  steam-chest  consists  of  the  cylinder  M,  valve  A, 
and  the  pistons  B  and  B' ;  the  pistons  are  connected,  sufficient 
space  being  allowed  between  them  for  the  valve  A  and  the 
steam-ports  f  and  f. 

The  valve  is  controlled  and  operated  by  the  steel  cam  C 
acting  on  steel  pin  D,  which  passes  through  the  valve  into 
exhaust-port  in  which  the  cam  is  located.  In  addition  to  this 
mechanical  operation  steam  is  alternately  admitted  to  and  ex- 
hausted from  the  ends  of  the  steam-chest  by  ports  e  and  e', 
operating  the  pistons  B  and  B'. 

OPERATION.  —  The  pump  being  at  rest  with  the  valve  A 
covering  the  main  steam-ports  f  and  f',  the  cam  C  holds  the 
valve  by  means  of  valve-pin  D,  so  that  ports  e  and  e'  admit 
steam  to  one  end  of  chest,  and  connect  the  other  end  with 
exhaust-port ;  the  steam  acting  on  valve-pistons  will  move  valve- 


122 


THE   SLIDE-VALVE   AND  ITS  FUNCTIONS. 


pistons  and  valve,  opening  main  ports  f  and  f,  admitting  steam 
to  one  end  of  steam-cylinder,  and  opening  the  other  end  to  the 
exhaust. 

If  the  valve  occupies  any  other  position,  the  main  ports  f 
and  f  will  be  opened  for  the  admission  and  exhaust  of  steam  ; 
consequently  it  is  evident  that  there  is  no  dead  point,  and  that 
the  pump  will  start  from  any  point  of  stroke. 


Fig.  79.     The  Davidson  Valve  Gear. 

Steam  being  admitted  to  cylinder  by  one  of  the  main  ports, 
as  f  in  illustration,  the  steam -piston,  cam,  valve,  etc.,  will  move 
in  direction  indicated  by  arrows.  The  first  move  of  the  cam 
will  be  to  oscillate  the  valve  preparatory  to  bringing  it  in  proper 
position  for  the  opening  of  the  auxiliary  steam-port  e  to  live 


THE   SLIDE-VALVE    ON  PUMPS. 


123 


steam,  and  e'  to  exhaust,  and  secondly  to  bring  the  valve  to  its 
closure  (mechanically)  slightly  before  the  end  of  the  stroke  of 
main  piston  (thereby  causing  slight  cut-off  and  compression), 
and  fully  opening  auxiliary  port  e  to  steam  and  e'  to  exhaust. 
By  the  admission  of  steam  to  one  end  of  the  chest,  the  other 
being  open  to  exhaust,  the  valve-pistons  will  move  valve  to  such 
position  as  will  allow  the  admission  and  exhaust  of  steam  to  and 
from  cylinder  for  the  return  stroke.  • 

The  main  valve  being  as  much  under  control  of  the  piston- 
rod  as  is  the  valve  of  an  ordinary  steam-engine  worked  by  an 
eccentric,  secures  a  positive  action,  pump  being  capable  of  start- 
ing from  any  position  and  maintaining  a  uniform  and  full  stroke. 

The  steam-piston  is  absolutely  prevented  from  striking  the 
cylinder-heads  by  virtue  of  the  mechanical  valve-closure. 


THE    CAMERON    PUMP    GEAR. 


There 
Short 


Fig.  80  shows  the  valve-gear  of  the  Cameron  pump, 
are  two  plain  tappet-valves,  one  in  each  cylinder-head, 
valve-stems  project  into 
the  cylinder ;  and  when 
the  piston  strikes  one  of 
these  the  valve  is  driven 
back     and      opens      an 
exhaust-passage        from 
the    corresponding   end 
of      the     chest-plunger, 
which     immediately     is 
shifted  under  the  action 
of    live    steam    on    the 
opposite     side     of     the 
plunger-head.     There  is 
a  small  hole  in  each  end          Fig'  8o'    The  Cameron  Pump  Gear' 
of  the  hollow  plunger ;  and  when  both  tappet-valves  are  closed 
the    steam,   passing  through   these   holes,   leaves    the   plunger 


124  THE  SLIDE-VALVE   AN^D   ITS  FUNCTIONS. 

entirely  surrounded  by  live  steam,  and  therefore  in  perfect 
balance  endwise,  until  the  piston  strikes  the  tappet  in  the 
opposite  cylinder-head,  when  the  valve-moving  operations  are 
repeated  in  the  opposite  direction.  The  space  back  of  the 
tappet-valve  communicates  with  the  steam-chest  through  a 
passage,  shown  in  dotted  lines ;  and  the  valve  is  therefore 
closed  by  steam-pressure  as  soon  as  the  piston  moves  back 
from  the  stem.  It  will  be  noticed  that  the  piston  closes  the 
exhaust-passage  before  the  end  of  the  stroke.  The  confined 
steam  forms  a  cushion  between  the  piston  and  the  cylinder- 
head,  but  a  little  passage  is  cut  in  the  cylinder  wall  through 
which  sufficient  steam  is  admitted  to  start  the  piston  on  the 
return  stroke. 

The  main  valve,  carried  by  the  chest-plunger,  is  shifted  in 
the  direction  the  piston  travels  at  the  end  of  the  stroke,  that  is, 
in  a  direction  opposite  to  that  of  a  common  slide-valve.  This 
valve  has,  therefore,  two  cavities,  each  of  which  alternately  puts 
the  cylinder  in  communication  with  the  steam-chest  and  the 
central  exhaust-port.  Steam  is  admitted  under  the  outer  valve- 
face,  as  shown  in  the  cut.  H  is  a  lever,  by  means  of  which  the 
steam-chest  plunger  may  be  reversed  by  hand  when  expedient. 

WORTHINGTON. 

Fig.  8 1  shows  one  side  of  a  Duplex  Pump  built  by  Henry 
R.  Worthington. 

Each  individual  pump  actuates  a  rocker,  which  drives  a  valve 
on  the  pump  on  the  other  side.  That  is,  the  rocker  of  one 
pump  and  the  valve  of  the  other  pump  are  constantly  in  gear. 
Each  valve  is,  therefore,  moved  independently  of  the  piston  in 
the  same  pump.  The  mutual  operation  is  such  that  one  pump 
must  always  be  half  a  stroke,  or  more,  behind  the  other.  At 
the  end  of  the  stroke  the  valve  covers  both  steam-ports  ;  but 
then  the  other  pump  is  at  mid-stroke,  with  its  ports  fully  uncov- 


THE   SLIDE-VALVE    ON  PUMPS. 


125 


ered,  and  thus  the  valve  is  always  promptly  carried  over  its  dead 
center  by  the  piston  of  the  other  pump. 

As  one  piston  is  about  half  a  stroke  ahead  of  the  other,  and 
the  valve-motion  should  be  the  same  on  both  pumps,  it  follows 
that  one  of  the  rockers  must  have  a  counter-arm  above  its  ful- 
crum to  move  the  valve  in  the  proper  direction. 

It  will  be  noticed  that  the  valve  is  confined  between  nuts  on 
the  valve-stem,  and  that  they  are  not  set  closely  against  the 
valve;  there  is  "lost  motion."  This  lost 

S*~^L. 

motion  is  necessary,  for  otherwise  the 
pump  might  not  make  full  stroke.  This 
is  explained  by  the  fact  that  the  first 
part  of  the  stroke  is  always  made  in  less 


Fig.  81.     The  Worthington  Duplex  Pump. 

time  than  that  of  a  corresponding  part  later  in  the  stroke ; 
wherefore  the  mid-point,  in  regard  to  time,  or  the  middle  of  the 
stroke-period,  comes  later  than  half-stroke.  The  lost  motion 
corrects  this  discrepancy  when  the  valve-motion  is  reversed. 

A  too  tightly  packed  water  piston  or  plunger  may  cause  a 
pause  at  the  commencement  of  the  stroke,  when  the  steam-ports 
are  nearly  covered,  and  consequently  a  later  reversal  of  the  valve- 
motion  on  the  other  side  ;  and  from  this  cause  the  working  of 


126  THE  SLIDE-VALVE  AND   ITS  FUNCTIONS. 

the  pump  may  become  somewhat  irregular.  The.  water-packing 
of  a  duplex  pump  should  always  be  in  good  condition. 

All  duplex  pumps  have  separate  exhaust -ports,  as  shown  in 
the  figure.  The  inner  ports  are  only  for  exhaust,  and  the 
outer  ones  for  live  steam.  After  the  exhaust-port  has  been 
opened,  there  remains  exhaust-steam  at  atmospheric  pressure  in 
the  cylinder  and  steam-passages ;  this  is  expelled  during  the 
return  stroke  until  the  exhaust -opening  is  covered  by  the  piston ; 
the  remaining  steam  is  then  compressed,  and  forms  a  steam 
cushion  between  the  piston  and  cylinder-head.  One  of  the 
exhaust-ports  is  always  covered  by  the  valve. 

Steam  cannot  be  used  expansively  in  single-cylinder  direct- 
acting  pumps,  because  there  is  not  enough  kinetic  energy  stored 
in  the  water  and  moving  parts  to  carry  the  piston  to  the  end  of 
its  stroke ;  but  it  may  be  used  expansively  in  multi-cylinder 
pumps,  for  the  pressure  in  each  individual  cylinder  may  not  vary 
greatly  in  a  compound  system,  when  the  admission  is  continuous 
during  the  entire  stroke.  The  result  is,  of  course,  a  considera- 
ble saving  in  steam.  The  speed  of  a  pump  is  regulated  by  throt- 
tling the  steam,  and  this  has  the  disadvantage  that  during  the 
dwell  at  the  end  of  the  stroke  the  steam-pressure  in  the  cylinder 
is  apt  to  rise ;  that  is,  at  a  point  where  the  increased  pressure 
does  no  good. 

In  a  triple  compound  pump  the  work  done  in  the  high- 
pressure  cylinder  is  only  a  small  part  of  the  whole  work  ;  and  it 
is,  therefore,  feasible  to  cut  off  the  steam  in  this  cylinder  before 
the  end  of  the  stroke. 

Fig.  82  shows,  in  section,  the  high-pressure  cylinder  of  a 
"Triple  Pump,"  built  by  Henry  R.  Worthington.  It  has  three 
cylinders,  connected  in  tandem,  and  it  is  on  the  Duplex  plan  ; 
each  set  of  valves  is  driven  by  a  rocker,  which  receives  its  mo- 
tion from  the  pump  on  the  other  side.  The  valves  are  all  of  the 
semi-rotary  kind.  They  are,  in  fact,  nothing  but  common  D- 
valves  on  concave  valve-seats.  They  are  located  under  the  cyl- 


THE   SLIDE-VALVE    ON  PUMPS. 


127 


inders  for  convenience,  and  it  is  a  superior  arrangement  for  drain- 
ing the  cylinders,  and  the  whole  arrangement  is  eminently  suita- 
ble for  a  simplified  valve-gear. 

There  are  two  steam-ports  and  two  exhaust-ports  in  the 
steam-chest,  arranged  as  the  ports  in  an  ordinary  duplex  pump  ; 
but  the  steam  and  exhaust  passages  are  united  into  one  passage 
before  entering  the  cylinder.  In  the  steam-passage  is  a  small 


Fig.  82.     The  Worthington  Triple  Gear. 

valve  which  cuts  off  the  admission  of  steam  before  the  end  of 
the  stroke.  The  point  of  cut-off  is  ordinarily  fixed,  but  it  can 
readily  be  changed  by  lengthening  or  shortening  the  rod  con- 
nections ;  that  is,  by  giving  the  cut-off  valves  more  or  less  lap. 

There  are  only  two  ports  in  the  intermediate  and  low-pressure 
cylinders ;  and  the  opening  into  the  low-pressure  cylinder  is  so 
located  that  the  piston  covers  it  before  the  end  of  the  stroke,  and 
is  thus  cushioned  on  the  imprisoned  steam. 


128  THE  SLIDE-VALVE   AND   ITS  FUNCTIONS. 


CHAPTER  VI. 

ANGULARITY  OF  CONNECTING-ROD  AND  ECCENTRIC-ROD. 
THE    ANGULAR    MOTION    OF    THE    CONNECTING-ROD. 

THE  motion  of  the  crank-pin  is  both  horizontal  and  vertical ; 
that  is,  it  may  be  dissolved  in  horizontal  and  vertical  components, 
parallel  with  the  center  line  of  the  engine  and  at  right-angles  to 
it ;  and  it  was  in  the  first  chapter  of  this  book  assumed  that  the 
horizontal  components,  or  the  projections  of  the  crank  move- 
ments on  the  horizontal  diameter  of  the  crank-circle,  represent 
exactly  the  movements  of  the  piston  in  a  horizontal  engine,  and 
no  account  was  taken  of  the  vertical,  or  up-and-down  motion  of 
the  crank-pin.  In  other  words,  it  was  assumed  that  the  horizon- 
tal distance  from  the  crank-pin  to  the  cross-head  pin  is  the  same 
at  any  point  of  the  stroke,  which  is  not  true ;  but  the  assump- 
tion is  permissible,  because  it  is  sufficiently  near  the  truth  for  a 
general  investigation  of  the  valve-action,  and  it  greatly  simplifies 
the  construction  of  valve-diagrams.  When  the  crank-pin  is  right 
on  the  center-line  of  the  engine,  its  distance  from  the  cross-head 
pin  equals  the  length  of  the  connecting-rod  ;  but  when  the  crank- 
end  of  the  connecting-rod  is  above  or  below  the  center-line,  the 
horizontal  distance  between  the  pins  is  shortened  more  or  less, 
according  to  the  inclination  of  the  rod.  The  piston  is,  therefore, 
always  nearer  the  crank-end  of  the  cylinder  than  has  been  as- 
sumed, except  in  its  two  terminal  positions  ;  and  in  equal  periods 
more  steam  is  admitted  during  the  head-end  stroke,  and  less  dur- 
ing the  crank-end  stroke.  The  piston  moves  faster  in  the  head- 
end part  of  the  cylinder  and  slower  in  the  crank-end  part ;  and 
when  the  crank  is  in  one  of  its  "  quarter  "  positions,  vertically 


ANGULARITY  OF   CONNECTING-   AND   ECCENTRIC-RODS.    129 

.above  or  below  the  shaft,  the  piston  has  either  passed  its  middle 
position  in  the  cylinder  or  it  has  not  yet  reached  it,  according  to 
which  way  it  is  moving.  In  constructing  the  valve-diagrams  it 
was  assumed  that  both  crank  and  eccentric  turned  at  a  uniform 
rate,  or  moved  through  equal  angles  in  equal  time,  which  assump- 
tion is  correct,  and  on  this  basis  coincident  positions  of  the  pis- 
ton and  valve  were  determined  ;  but,  as  no  attention  was  paid  to 
the  angularity  of  the  connecting-rod,  some  correction  is  neces- 
sary to  present  the  piston-motion  in  its  exact  relation  to  the 
invariable  time  basis,  and  to  suggest  such  changes  of  the  valve 
and  valve-motion  as  will  cause  it  to  operate  in  closer  harmony 
with  the  irregularities  of  the  piston-motion. 

Hitherto  one  side  of  the  piston  only  was  considered,  on  the 
assumption  that  there  was  no  difference  in  the  piston-velocity 
from  either  cylinder-head,  but  now  both  sides  of  the  piston  will 
be  considered  conjunctively.  A  double-acting  cylinder  repre- 
sents two  single-acting  cylinders,  as  it  were,  and  it  appears  that 
the  piston-velocity  is  not  the  same  in  both  of  these.  The  main 
difficulty  consists  in  equalizing  the  cut-offs  on  both  sides  of  the 
piston  when  steam-admission  and  cut-off  is  regulated  by  a  single- 
valve  or  conjugate-valves;  and  this  is  the  condition  assumed  in 
the  following. 

In  a  great  number  of  engines  a  slight  inequality  of  the 
cut-offs  is  of  no  consequence,  and  no  attention  is  paid  to  it,  or 
it  is  partly  corrected  by  the  valve-setting.  No  power  is  gained 
by  equalizing  the  cut-offs,  and  no  steam  is  saved  by  it.  The 
"most  economical  point  of  cut-off"  is  a  vague  conception,  and 
the  variation  due  to  the  angularity  of  the  connecting-rod  is  not 
sufficient  to  have  any  practical  bearing  on  this  point  ;  but  ine- 
quality of  cut-off  has  unquestionably  some  disturbing  effect  on 
the  speed  of  the  engine,  and  this  may  be  of  some  consequence 
in  compound  or  high-expansion  engines. 

The  angularity  of  the  eccentric-rod  has  a  disturbing  effect 
on  the  steam-lead  which  may  become  of  some  consequence  in 


130  THE  SLIDE-VALVE   AND  ITS  FUNCTIONS. 

shifting  eccentric-engines,  and  Professor  Sweet's  method  of 
obviating  it  will  be  explained. 

The  circle  in  Fig.  83  represents  the  path  of  the  crank-pin, 
and  the  direction  of  motion  is  shown  by  the  arrow.  The  circle 
may  also  represent  the  time,  or  period  of  one  revolution  of  the 
crank  ;  and  as  the  rotative  speed  is  supposed  to  be  uniform,  any 
part  of  the  circle,  measured  in  degrees  or  by  its  center  angle, 
will  represent  a  proportionate  period,  or  interval  of  time ;  and 
the  center-line  of  the  crank,  like  the  hand  of  the  clock  turning 
on  its  dial,  will  mark  fractional  parts  of  the  period  of  revolu- 
tion, in  strict  conformity  with  its  angular  movements. 

While  the  crank  is  turning,  the  valve  slides  on  the  valve-face, 
and  is  supposed  to  open  and  close  the  ports  at  the  proper 


Fig.  83 

Fig.  83. 

moments  for  an  equal  steam  distribution  at  both  cylinder-ends, 
or  at  both  sides  of  the  piston  ;  and  the  instant  this  occurs,  or 
should  occur,  may  be  marked  on  the  crank-circle,  as  shown. 

The  diameter  of  the  circle  in  Fig.  83  may  represent  the 
stroke  of  the  piston  toward  the  shaft  from  left  to  right  and 
returning  in  the  opposite  direction  ;  and  it  may  represent  for- 
ward- and  return-stroke  for  both  cylinder-ends,  or  for  both 
single-acting  cylinders,  as  it  were.  Considering  the  head-end 
stroke,  when  the  crank-pin  is  at  point  2  the  piston  is  at  the 
middle  of  its  stroke ;  for  if  the  connecting-rod  be  swung  down 
from  this  point,  without  moving  the  cross-head,  it  will  strike 
the  center  of  the  circle,  as  shown.  Therefore,  if  steam  is  to  be 
cut  off  exactly  at  half-stroke,  it  must  occur  when  the  crank  is 


ANGULARITY  OF  CONNECTING-   AND   ECCENTRIC-RODS.    181 

in  position  2,  or  the  valve  must  close  the  port  at  the  moment 
the  crank  arrives  at  point  2  ;  and  in  that  case  arc  1-2,  marks 
the  admission-period.  Considering  the  crank-end,  the  port 
should  be  closed  when  the  crank-pin  is  at  point  6  ;  and  in  this 
case  arc  5-6  represents  the  period  of  admission,  which  is  longer 
than  the  period  of  admission  at  the  head-end.  The  points  of 
admission  i  and  5  are  made  diametrically  opposite  in  order  to 
get  equal  lead  at  both  ends  of  the  cylinder. 

Now  the  eccentric  turns  in  unison  with  the  crank;  and  if 
the  points  marked  on  the  crank-circle  be  turned  forward, 
through  an  angle  equal  to  the  angular  advance  of  the  eccentric, 


Fig.  84. 

they  will  be  in  their  proper  positions  for  the  eccentric-circle. 
Thus  Fig.  84  represents  the  eccentric-circle.  V  is  the  angle  of 
advance,  and  the  figures  along  the  circumference  mark  the 
instants  of  opening  and  closing  the  ports,  as  in  Fig.  83,  but  with 
the  eccentric-radius  as  a  pointer. 

If  the  valve-end  of  the  eccentric-rod  moves  in  a  straight 
line  which  passes  through  the  center  of  the  shaft,  the  chords 
1-2  and  5-6  must  be  parallel,  as  shown  in  the  first  part  of  the 
book  ;  and  which  also  will  appear  from  a  mere  inspection  of 
Figs.  84  and  85,  if  it  be  remembered  that  the  valve-end  of  the 
rod  must  be  at  the  same  point  when  the  valve  opens  and  closes 


132  THE  SLIDE-VALVE   AND   ITS  FUNCTIONS. 

the  port ;  but,  referring  to  Fig.  83,  it  will  be  observed  that  if 
points  2  and  6  are  fixed,  chords  1-2  and  5-6  cannot  be  parallel 
without  changing  the  locations  of  points  i  and  5  in  opposite 
directions.  It  is,  therefore,  not  possible  to  equalize  the  cut-offc 
with  the  ordinary  eccentric-rod  motion  without  introduckg 
unequal  leads. 

Earlier  cut-off  can  be  obtained  in  the  head-end  stroke  by  in- 
creasing the  head-end  lap,  and  later  cut-off  may  be  obtained  in 
the  crank-end  stroke  by  decreasing  the  crank-end  lap.  If  the 
valve  admits  steam  over  the  outside  edges,  both  these  changes 
may  be  made  by  lengthening  the  valve-rod  ;  and  xshortening  it 
has  the  same  effect,  if  steam  is  admitted  over  the  inside  port- 
edges,  or  if  the  valve  is  moved  by  a  counter-arm  on  the  rocker  ; 
but,  in  any  event,  such  change  involves  less  lead  at  the  head-end 
and  more  at  the  crank-end.  If  the  valve  has  ample  lead,  a  little 
change  either  way  will  not  be  of  much  consequence ;  but  if  there 
is  little  or  no  lead  or  negative  lead,  unequal  steam-laps  are  mor%e 
objectionable;  and,  as  the  port-opening  equals  half  the  travel, 
minus  the  lap,  the  opening  for  early  cut-offs  may  become  unduly 
restricted  at  one  end  of  the  cylinder.  This,  however,  may  under 
certain  conditions  be  partly  avoided  by  using  a  short  eccentric- 
rod,  as  will  presently  be  explained. 

THE    ANGULAR    MOTION    OF    THE    ECCENTRIC-ROD. 

The  up-and-down  motion  of  an  eccentric  of  a  horizontal  en- 
gine draws  the  eccentric-rod  towards  the  shaft,  as  shown  in  Fig. 
85,  where  the  rod  is  represented  disproportionally  short  for  the 
sake  of  clearness.  To  correct  this,  the  immediate  valve  connec- 
tions must  be  lengthened  if  the  valve  moves  in  the  same  direc- 
tion relative  to  the  crank-shaft  as  does  the  eccentric-rod  pin,  and 
shortened  if  the  motion  is  reversed  by  a  counter-arm.  In  other 
words,  the  head-  and  crank-end  laps  are  made  unequal. 

The  angular  vibration  of  the  eccentric-rod  gives  a  quicker 
motion  to  the  valve  at  one  end  of  its  travel  and  a  slower  motion 


ANGULARITY  OF  CONNECTING-   AND   ECCENTRIC-RODS.    133 

at  the  other  end  ;  and  the  period  of  admission  is,  therefore, 
under  certain  conditions,  shortened  at  the  head-end  and  length- 
ened at  the  crank-end  without  changing  the  laps.  The  result  is 
more  equal  cut-offs  with  equal  port-openings ;  but  if  the  admis- 
sion periods  must  be  diametrically  opposite,  the  inequality  of 
these  periods  must  necessarily  make  the  leads  unequal. 

In  order  to  obtain  results  as  here  stated,  the  steam  must 
either  be  admitted  over  the  inside  port-edges,  or  else  the  valve 
must  be  moved  by  a  counter-arm  rocker  ;  otherwise  the  inequal- 
ity of  laps  and  port-openings  will  be  increased  instead  of  di- 
minished. 


Fig.  85. 

The  length  of  the  eccentric-rod,  compared  with  the  throw  of 
the  eccentric,  is  generally  too  great  to  make  the  influence  of  its 
angular  vibration  of  much  consequence ;  but  if  the  facts  here 
mentioned  are  fully  understood,  they  may  occasionally  be  used 
to  advantage  by  a  discriminating  designer. 

If  the  valve-end  of  the  eccentric-rod  is  guided  by  a  common 
rocker-arm,  it  may  become  slightly  elevated  at  the  middle  of  its 
travel,  which  has  a  quite  inappreciable  effect  in  the  direction  of 
later  release  and  compression  if  the  engine  is  "running  over," 
and  a  depression  towards  the  end  of  its  travel  has  the  opposite 
effect  on  the  lead  and  cut-off,  but  the  effect  in  either  case  is 
practically  nil. 


134  THE   SLIDE-VALVE  AND   ITS  FUNCTIONS. 


STEAM-    AND    EXHAUST-LAPS. 

As  the  diameter  of  the  crank-circle,  Fig.  83,  represents  the 
forward  stroke  and  the  return-stroke  for  both  ends  of  the  cylin- 
der, points  of  cut-off,  release,  and  exhaust-closure  may  be  located 
on  this  diameter  at  equal  distances  from  the  ends ;  and  by  strik- 
ing arcs  with  radius  equal  to  the  length  of  the  connecting-rod, 
as  shown,  the  corresponding  crank-positions  are  located. 

Points  i,  2  and  3,  4  mark  admission  and  cut-off,  release,  and 
exhaust-closure  positions  of  the  crank-pin  for  the  head-side  of  the 
piston,  and  5,  6  and  7,  8  mark  corresponding  positions  for  the 
crank-side.  Ordinarily  all  the  chords  connecting  each  pair  of 
these  points  must  be  parallel,  and  to  suit  this  requirement,  the 
points  must  be  rearranged,  according  to  the  best  judgment  of 
the  designer. 

The  distances  from  the  center  of  the  circle  to  the  chords, 
measured  by  the  proper  scale,  give  the  required  laps  ;  and  it  will 
be  noticed  that  release  and  compression  may  be  very  nearly 
equalized  for  both  cylinder-ends  by  suitably  proportioned  ex- 
haust-laps. The  exhaust-lap  for  the  crank-end  becomes  larger 
than  that  for  the  head-end,  and  the  only  objection  to  this  is  the 
reduction  of  port -opening  at  the  crank-end.  If  the  exhaust-laps 
are  made  equal,  it  is  impossible,  with  the  ordinary  valve-gear,  to 
make  the  compression  curves  on  the  indicator  card  equal  without 
greatly  disturbing  the  lead  and  cut-off. 

EQUALIZING    BOTH    LEAD    AND    CUT-OFF. 

If  the  cut-offs  are  to  be  equal  on  both  sides  of  the  piston 
without  changing  the  leads  the  periods  of  admission  cannot  be 
diametrically  opposite.  Any  period  may  be  changed  either  way 
by  turning  the  eccentric  on  the  shaft ;  but  in  that  event  all  the 
periods  will  be  changed  conjunctively.  Instead  of  turning  the 
eccentric  on  the  shaft,  the  eccentric-rod  may  be  turned  ;  for  the 
eccentric-action  is  in  the  direction  of  the  rod ;  and  if  the  rod  is 


ANGULARITY  OF  CONNECTING-  AND  ECCENTRIC-RODS.    185 

turned  in  a  different  direction,  the  points  marking  opening  and 
closing, of  the  ports  will  be  turned  the  same  amount  in  the  same 
direction  on  both  the  eccentric  and  crank-circle  ;  and  if  the  valve- 
end  of  the  rod  receives  a  reciprocating  angular  motion  relative 
to  the  crank-shaft,  there  will  be  a  corresponding  angular  dis- 
placement of  the  conjugate  points,*  according  to  the  instantane- 
ous angular  displacement  of  the  rod  ;  and,  therefore,  by  suitably 
guiding  the  end  of  the  eccentric-rod,  the  admission-periods  can 
be  properly  timed  for  equal  leads  and  equal  cut-offs  on  both  sides 
of  the  piston. 

The  mean  direction  of  the  eccentric-rod  for  any  period  of 
open  or  closed  port  is  represented  by  a  straight  line  passing 
through  the  center  of  the  corresponding  arc  on  the  eccentric 
circle  and  at  right  angles  to  the  chord.  If  the  valve-end  of  the 
eccentric-rod  be  guided  by  an  inclined  rocker-arm,  as  shown  in 
Fig.  84,  the  mean  direction  of  the  rod  for  the  admission 
period  1-2  will  be  different  from  its  mean  direction  for  the 
admission-period  5-6,  as  indicated  in  the  figure  ;  it  being  under- 
stood that  when  the  eccentric  is  at  either  point  I  or  2,  the 
pin  is  at  point  1 2,  and  when  the  eccentric  is  at  5  or  6  the  pin  is 
at  point  56  —  these  being  the  coincident  positions  of  the  eccen- 
tric-rod pin  when  the  steam-edges  of  valve  and  port  come  to- 
gether at  the  head-  and  crank-end  respectively. 

Now,  if  by  variation  of  the  mean  inclination  of  the  rod  for 
points  12  and  56  respectively,  the  angle  of  variation  equals  the 
angle  of  convergence  of  the  admission-chords,  1-2  and  5-6,  in 
Fig.  83,  the  cut-off  may  be  fixed  at  exactly  half  the  stroke 
either  way  by  giving  the  valve  proper  laps,  and  without  disturb- 
ing the  leads.  The  laps  are  determined  by  the  distance  from 
the  center  of  the  rocker-arm  arc  to  points  12  and  56  respec- 
tively ;  and  the  port-openings  are  determined  by  the  distance  of 
these  points  from  the  ends  of  the  arc. 

If  the  points  on  the  eccentric-circle  are   correctly  spaced, 

*  Points  i,  2  and  3,  4,  etc.,  are  for  obvious  reasons  called  conjugate  points. 


136  THE   SLIDE-VALVE   AND   ITS  FUNCTIONS. 

points  12  and  56  may  be  located  by  striking  arcs  with  a  radium 
equal  to  the  length  of  the  eccentric-rod  from  the  corresponding 
points  on  the  circle  ;  and  for  the  equalization  of  lead  and  cut-off, 
the  end  of  the  rod  may  be  guided  in  any  manner  whatever  if  it 
passes  through  points  12  and  56;  but  the  rocker-arm  affords 
the  only  satisfactory  means  of  accomplishing  this.  The  rocker- 
fulcrum  may  be  located  above  the  eccentric-rod ;  but  this  would 
make  the  port -openings  unequal,  as  shown  in  Fig.  84,  while  in 
the  other  position  the  port-openings  may  be  equalized  by  using 
a  rocker-arm  of  the  proper  length.  The  exhaust-periods  will  be 
advanced  a  trifle  on  account  of  the  upward  curvature  of  the 
rocker-arc  ;  that  is,  they  will  come  a  trifle  later  in  the  stroke, 
which  may  be  an  advantage  rather  than  otherwise.  The  curva- 
ture of  the  arc  has  practically  no  effect  on  the  equalization  of 
release  and  compression,  which  depends  on  the  correct  propor- 
tioning of  the  exhaust -laps. 


THE    INCLINED    ROCKER    FOR    SHIFTING-ECCENTRIC    ENGINES. 

When  the  inclined  rocker  is  applied  to  variable  cut-off 
engines  it  cannot  equalize  the  cut-offs  at.  all  points  of  the  stroke  ; 
for  the  equalization  depends  on  the  angle  between  the  two  mean 
directions  of  the  eccentric-rod  for  the  head-end  and  crank-end 
admission-periods,  as  shown  in  Fig.  84.  As  the  laps  of  the 
valve  are  unchangeable,  the  distance  between  points  12  and  56 
is  practically  constant  for  all  cut-offs ;  and  the  rocker-arm  can, 
therefore,  only  equalize  the  cut-offs  for  two  or  four  points  on 
the  crank-circle,  which  give  the  proper  convergency  or  mutual 
inclination  of  the  admission-chords.  This  convergency  is  great- 
est for  the  mid-stroke  cut-off,  and  it  decreases  by  earlier  and 
later  cut-offs,  and  becomes  practically  nil  at  the  beginning  of 
the  stroke.  If,  for  example,  the  rocker-fulcrum  be  so  located  as 
to  equalize  the  cut-offs  at  one-fourth  of  the  stroke,  the  earlier 
cut-offs  will  be  too  early  at  the  head-end  and  too  late  at  the 


ANGULARITY  OF  CONNECTING-   AND   ECCENTRIC-RODS.   137 

crank-end ;   and    an  ordinary  rocker-arm  will  give  very  nearly 
equal  cut-offs  near  the  beginning  of  the  stroke. 


EQUALIZING    THE    LEAD    IN    SHIFTING-ECCENTRIC    ENGINES. 

The  angular  vibration  of  the  eccentric-rod  draws  the  valve 
towards  one  end  of  the  steam-chest,  and  this  can  be  provided 
for  by  making  one  lap  a  little  longer  than  the  other ;  but  if  the 
throw  of  the  eccentric  varies,  as  when  it  is  shifted  across  the 
shaft,  the  lead  cannot  be  equalized  in  this  manner  for  more  than 
one  proportion  of  cut-off,  but  nearly  equal  leads  at  both  cylinder- 
ends  may  be  obtained  for  the  whole  range  of  cut-off  by  means 
of  the  inclined  rocker,  as  will  now  be  explained. 


Fig.  86. 

If  steam  is  admitted  over  the  inside  port-edges,  the  eccen- 
tric must  be  located  on  the  crank-side  of  the  shaft ;  and  in  that 
case  Fig.  86  represents  the  eccentric-circle,  and  the  rocker  will, 
in  its  middle  position,  be  leaning  toward  the  cylinder-end,  as 
shown.  Let  the  center  of  the  eccentric  be  at  B  and  A  at  the 
commencement  of  the  head-end  stroke  and  the  crank-end  stroke 
respectively,  and  let  the  annexed  short  curves  represent  the 
path  of  the  center  of  the  eccentric,  when  it  is  moved  across 
the  shaft ;  then  if  the  corresponding  positions  of  the  eccentric- 
rod  pins  are  at  D  and  C  respectively,  and  if  lines  from  these 
points  to  the  middle  points  of  curves  B  and  A  are  parallel,  it 
will  be  seen  that  if  the  rod  is  swung  from  the  outer  to  the 


138 


THE   SLIDE-VALVE   AND   ITS  FUNCTIONS. 


inner  end  of  the  curved  path  in  either  position,  points  D  and  C 
will  be  shifted  very  nearly  the  same  amount,  in  opposite  direc- 
tions, and  thus  nearly  equal  lead  may  be  obtained  for  both  ends 
of  the  cylinder,  irrespective  of  the  points  of  cut-off.*  It  should 
be  observed  that  the  valve-end  of  the  eccentric-rod  must  be 
angularly  advanced,  relative  to  the  crank-shaft  while  moving 
toward  the  shaft ;  and  in  order  that,  under  this  condition,  the 
cut-offs  may  be  equalized  for  some  intermediate  points  in  the 
stroke,  it  is  necessary  that  the  admission-period  for  the  head-end 
be  on  the  rocker-side  of  the  eccentric.  The  valve  must,  there- 


Fig.  87. 

fore,  either  admit  steam  over  the  inside  edges,  or  else  the 
motion  from  the  eccentric  must  be  reversed  by  means  of  a 
counter-arm  on  the  rocker.  By  such  arrangement  the  cut-offs 
may  become  more  equal  than  with  the  ordinary  rocker ;  but  if 
the  crank-end  admission-period  is  on  the  rocker-side  of  the 
shaft  the  inequality  of  the  cut-offs  will  be  greater  than  when  a 
common  rocker  is  used.  Also  note  that  equal  port-openings 
cannot  be  had  unless  the  rocker-fulcrum  is  behind  the  rocker- 
arm,  in  the  direction  of  rotation  of  the  eccentric  ;  that  is,  if  we 
imagine  the  rocker  swung  around  the  shaft. 

In  the  Straight-Line  engine  steam  is  admitted  over  outside 

*  Professor  Sweet  explained  this  to  the  writer  in  1882  by  drawing  seven  chalk-lines  on  a 
blackboard. 


ANGULARITY  OF   CONNECTING-   AND   ECCENl^RIC-RODS.    139 

port-edges,  and  the  form  of  the  rocker  used  on  some  of  these 
engines  is  indicated  in  Fig.  87.* 

UNEQUAL    LAPS    FOR    A    VARIABLE    CUT-OFF    ENGINE. 

It  is  questionable  whether  any  attempt  should  be  made  to 
equalize  the  cut-offs  in  shifting-eccentric  engines  by  varying  the 
laps  without  the  inclined  rocker ;  for  any  considerable  dissimi- 
larity of  the  laps  will  have  a  decidedly  bad  effect  on  the  early 
cut-offs  and  early  leads,  on  account  of  the  short  travel  and 
small  port-opening  ;  but  the  release  and  compression  may  be 
equalized  for  both  sides  of  the  piston,  to  a  great  extent,  by 
making  the  head-end  exhaust-lap  smaller  and  the  crank-end  lap 
longer.  In  the  early  cut-offs,  the  valve  opens  and  closes  for  the 
exhaust  nearer  the  middle  of  the  piston-stroke,  and  the  greater 
angularity  of  the  connecting-rod  at  these  points  neutralizes,  to 
some  extent,  the  effect  of  reduced  travel  as  far  as  the  unequal 
laps  are  concerned ;  and  as  the  smallest  exhaust-opening  is 
never  much  less  than  the  amount  of  steam-lap,  the  conditions 
are  altogether  favorable  for  an  equalization  of  the  exhaust- 
action  by  means  of  the  exhaust-laps. 

The  graphical  methods  used  or  suggested  in  connection  with 
the  subject-matter  of  this  chapter  are  useful  in  a  wider  sense, 
as  illustrative  of  a  simple  and  rational  method  for  the  exact  de- 
termination of  the  steam  distribution  in  the  cylinder,  the  lapse 
of  the  valve,  and  the  port-openings  a  method  which  is  generally 
applicable,  and  which  involves  few  artifices  and  no  curve-tracing, 
and  therefore  should  commend  itself  to  the  practical  designer. 

*  The  inclined  rocker  was  discussed  by  Mr.  F.  A.  Halsey  in  the  A  me  rican  Machinist  for 
February  28  and  March  14,  1889, 


INDEX. 


[Illustrations  are  indicated  by  an  asterisk  (*) 


Admission 

Period  of,  5*,  8,  g,  ic 


PAGE 

...       9,  10 

12*,    IS,    16,    21, 

131,  '35.  '38 

Point  of 9»  "i  I2* 

Allen,  John  F 75 

Allen  Locomotive  Valve,  the 35* 

Allfree  Valve  Gear,  the 57 •  58* 

Angle  of  Advance,  5*,  10,  n,  12*,  14*,  15,  l6»  2I 
Angularity  of  Connecting-rod,  n,  128,  129,  130* 


Of  Eccentric-rod 


.6,  129,  132,  133* 


Ball,  Frank  H. .    . 41 

Telescopic  Valve,  the 41* 

Balanced  Area 43*,  45* 

Balancing  a  Common  I)-valve  .   42,  43*,  44,  45* 

Balance,  the  Thomas 45* 

Balanced   Valve    with    Independent    Cut- 
off      101* 

Begtrup's  Eccentric 97.99* 

Blake  Single  Pump,  the •    •     .117* 

Buckeye  Flat  Valve,  the 103* 

Round  Valve,  the 106* 

Valve  Gear,  the 102,  104* 

Vibrating  Cut-off  .     .     .     .     in,  112*,  113* 

Cameron  Pump-gear,  the 123* 

Clark,  D.  K 27 

Clearance,  27,  28,  35,  52,  53*,  54,  63*,  64*,  80, 

in* 

Combination  Valve,  Limitations  of  the,  16,  17 
Compound  Rocker,  the  Buckeye  ....  70* 

Valves  .  .  •  50,  51*,  52, 53*, 54, 55.  56* 

Compression n,  12*,  17,  27 

Condenser,  Effect  of 27,  43 

Connecting-rod,  Angularity  of,  n,  128, 129,  130* 

Cooling  Surface 34>  35.  76 

Corliss,  George 31 

Corliss  Gear,  Limitations  of  ....  65,  66 

Setting  of  the 72 

Corliss  Valves i ,  62*,  63* 

Dimensions  of 7l 

Motion  of 62*,  63*,  64,  65 


PAGE 

Creeping  Steam 43 

Cut-off io,  n,  12*,  16,  17 

Eccentric  Journal  on  Engine  Shaft,  90, 91 , 92 

Equalized 131 

Gonzenbach,  the 81* 

Independent 80 

Meyer's 85* 

Point  of 5*,  11,12*,  16 

Range  of 25 

Single  Valve 23 

Square 22,  31 

Unequalityof 129 

Varied  by  Rotating  Eccentric,  90*,   93*,  0* 

Cut-t  ff  Valves,  80,  81*,  85*,  90*,  9^*,  9&*,  «"*, 
103*,  106*,  109*;  i  io*,  112*,  113* 

On  Back  of  Main  Valve 83 

On  an  Anchor  Plati 83 

On  a  Stationary  Valve  Seat    ....      8r 

Simple  Form  of 81,82* 

With  Constant  Travel  on  Main  Valve, 

99,  IOT*,  103*,  106*,  112* 
Worked  by  Means  of  a  Rocking  Link, 

106,  107* 

Cylinder,  Double  Acting 4,  229 

Single  Acting 4,  5°*i  53* 

Dash-pot  Action 65,66 

Dead  Center 9,  « 

Setting  Engine  on -      32 

Davidson's  Pump  Gear 121,122* 

Dean  Brothers'  Single  Pump  Gear    .     119,  120* 
Double  Ported  Valves      .     .     34*,  39*,  4'*,  63* 

Duplex  Pump 125* 

D-valve x,  2*.  4,  7,  8,  '8,  41,  96 

Diagram 12* 

Cylindrical 78*.  127* 

Limitations  of  the 16,  17 

On  Pumps,  the "5 

Double-Acting  Engine 4,8 


Eccentric 5,9," 

Eccentricity  of 6 


141 


142 


INDEX. 


PAGE 

Eccentric,  At  Half-Throw 7 

Exhaust 8,  70 

Begtrup's 97,  99* 

Radius  of 6 

Rod,  Angularity  of  .  .  .6,  129,  132,  133* 

Single 17 

Shiftable 16,  21 

Steam 8,  69 

Throw  of 6,  16 

Rotative  on  Shaft .  .  83,  90,  103,  112,  113 

Exhaust  Cavity 2*,  8,  17,  20,  4i 

Eccentric 8,  70 

Clearance 4 

Closure 12,  17 

Edge I7 

Lap 2*.  3,7,8,9,  17 

Negative  .  * 3,  56* 

Lead 10,  12 

Line ig 

Opening 8,  16,  38 

Passage 18 

Period 5*,  8,  9,  12*,  15,  16 

Port 3,  7,  8,  62*.  63* 

Valve .  7,21,37,  in* 

Face  of  Valve a. 

Free  Expansion 3I 

Four-valve  Systems      . 61 

Friction  of  Steam    .  10 


Gonzenbach  Cut-off,  the 

Valve  Diagram  of 

Governor,  Shaft,  37,  50,  53,  92,  93,  99, 

no 

Vertical 

Gridiron  Valves  with  Independent  Cut-off, 
Gridiron  Valves  .  75,  76*,  96*  109*,  112,* 

Halsey,  F.  A 

Hill,  Edward  K .     .     .     . 

Hill  Valves,  the 

Ideal  Engine,  Valves  of  the     .    .    .  47* 

Independent  Cut-off 

On  Four-valve  Engines 

Improved  Slide-valves 

Inclined    Rocker    for    Shifting- Eccentric, 
!36,  137"*, 
Indicator  Diagram,  Theoretical     .     ».;,... 14, 

Inside  Lap ...»:^ 

Intervening  Steam  Pressure      ..    .  .,,,.*•,  .; 

Knowles' Pump-gear    .    .    .    .  v'r  :!' 

LaP" 2*,5*.7,9,»,-i« 

On  Separate  F.xhau&t  Va'.ve   .     . 


81* 
83* 
109, 

,  112 

107 
96 

113* 

139 
76 

76* 

,48* 
80 
1 08 
34 

138* 

*24 

3 

44 


PAGE 

Lap,  Travel  and  Port-Opening     .     .     .     24,  25 

Steam  and  Exhaust 

Unequal    .... 
Lapless  Valves    .     .     . 

Leakage  Loss 

Lead 

Angle 

Negative 

Notes  About 

Variable 2.*,  26,  29*,  3I 

Limitations  of  the  Combination  Valve  .     .       if, 

Of  the  Corliss  Gear   .     . 

Links 

Locomotive  Valves,  Motion  of 
Low  Receiver  Pressure    . 


1     •     •     '34 
i33,  134,  135,  139 

n 

32 

•  10,   12*,  16,  21* 
26 

•  •     •     •      10,  27 


65,66 

29*,  72,  ,07* 
..  28,  29* 


McEwen  Valve,  The     .......    3g* 

Mclntosh  &  Seymour  Valves,  The    .     108,  109* 
Meyer  Cut-Off,  The     ........     gs* 

Limitations  of   .......  .   .  g^, 

Multiporting    ...........      3I 

Negative  Lap  on  Cut-Off  Valves,  82*,  86*,  87, 

QJ*,  100*,  101*,  104* 
Negative  Exhaust-Lap     ......     3)  56* 

Lead 


Outside-Lap 

Oscillating  Valves 


19*,  20 


19,    43 


Piston-Valves   ........  i,46*,  47* 

With  Independent  Cut-Off     .     .     105,106* 

Piston  Velocity   .     .     .:'.;'„    .     .     .     .    22,  25* 

Period  of  Revolution   ........        n. 

Of  Steam  Distribution    ......       IX 

Port   .....  ...... 

Area  of 
Contraction  of 
Formula  for 

Port-Opening.     .     •  7,  9,  '5,  '7,  19,*  22,  23,  25* 
Equality  of    .     .     .     .......     13g 

Initial  ............       I0 

Variation  of  .........   24,  25* 

Porter  Allen  Engine.  Valves  of  the    .     .     .     72* 

Pressure  Relieving  Device    .     .     .     42,  43*,  45* 
Plate    ........   36*,  38,  73*,  74 

Exhaust  ..........      3g 

Pumps,  Slide-  Valve  on     .......     nj 

Blake,  the     ..........  u7* 

Cameron,  the    .........  123* 

Davidson,  the   .......     1^1,  122* 

Dean  Brothers'      ......     ng,  j20* 

Knowles'       ..........     I2r 

Worthington,  the  ......     i24,  125* 

Triple  Compound  ......     126,  127* 


143 


PAGE 

Receiver  Press  are,  High 5i 

Low 43 

Relation  Between  Lap  and  Travel     .     .    15,21* 

Release.  Point  of 12,  23,  24 

Early 24 

And   Compression,   Constant,  21*,  23,  38, 

57,  So 

Relieved  Area 43 

Reversal  of  Crank  Motion Ij 

Revolution,  Period  of 9,  16 

Rice  &  Sargent,  Valves  Designed  by      .     .    64* 
Richardson  Balanced  Valve,  the    ....      44 

Rider,  A.  K 90 

Cut-Off ,  the 89,  90 

Rocker,  Compound 103,  .104* 

Counter-Arm 30,  133,  138* 

Inclined 135,  136,  137*,  138* 

Robinson,  S.  W 43 

Russell  Engine,  Valves  of  the  .     .     .  no*,  in* 

Semi-Rotary  Valves     .     i,  62*,  63*,  64*,  78* 
Single- Valve  Gear,  Allfree,  the     .     .     .   57,  58* 

Single-Acting  Cylinders 4,  50*,  53* 

Slide-Valve,  the  Common 1,2* 

Cylindrical    ....      i,  62*,  63*,  64*,  78* 

Simplest  Form  of 4,  5*,  8 

Spring-Rings 47,48,106* 

Steam,  Creeping 43,45 

Admission 7 

Friction  of     .     . jg 

Dry,  Wet,  or  Superheated ig 

Eccentric 8 

Lap 2*,  3, 7,  ii,  12* 

Lead 10 

Line ig,  3I 

Port 2*,  3,  18 

Passages ,8,  32 

Ports,  Supplementary,  17,  32,  35*,  36*,  46* 
And  Exhaust  Edges,  Transposition  of,  38 
Velocity  of ig 


Valve 


Straight  Line  Balanced  Valve,  the     .     .     .    36* 

Variations  of 38,  39* 

Sweet,  John  E 15,130,138 

Sweet's  Valve  Diagram     ....     14*,  15,  2i* 

Telescopic  Valve 4,» 

Thomas,  W.  J 44 

Thomas  Balance,  the 44>  45* 

Thomson,  J.  W IC2 


Throw  of  Eccentric 6,  12*,  16 

Travel  and  Lap 2i*,  22 

of  Valve 9)  12*t  1S>  ,7 

Unequal  Laps  for  Variable  Cut-Off  Engines, 

139 

Valve  Dimensions 20 

Face  of     2 

Seat  of 2 

Motion  in  Relation  to  Piston  Motion  .        9 

Without  Lap IX 

Diagrams,  Primitive J2* 

Sweet's 14*  f  2i* 

For  Corliss  Engines     .     .     .      67*,  70* 

Simple  Cut-Off 82* 

For  the  Gonzenbach  Cut-Off    .     .    83* 

For  Meyer's  Cut-Off 86* 

For  Rotative  Adjustment,  91*,  92*,  94* 

For  Link  Connection 107* 

Combined  Steam  and  Exhaust     .     .  16*  17* 

For  High-Speed  Engines,  16,  35*,  36,*  39*, 

4i*,  43*,  45*,  46*,  47*,  48*,  50*,  51*,  53*, 

56*,  58* 

Flat  Balanced 36*,  39*,  73* 

Leakage  of 32 

Separate  for  Steam  and  Exhaust,  21,61,63*, 
73*,  76* 

Unbalanced 17 

Cut-Off 80 

Expansion 80 

Gridiron    ....     75,  76*,  96*,  109*,  113* 
Of  the  Straight- Line  Type  .     .     .     .   37,39* 

Compound 50,  51*,  53,  56* 

Designed  by  Messrs.  R ice  &  Sargent, 63, 64* 

Variable  Valve  Travel 15 

Vauclain  Valve,  the 54,  56* 

Velocity  of  Steam 19 

Piston 25* 

Westinghouse  Standard  Valve,  The,  49, 50* 

Compound  Valve,  the     , 53* 

Wheelock  Valves,  the 78*,  79 

Wiredrawing 31,  37 

Worthington,  Henry  R 116 

Duplex  Pump,  the 124,  125* 

Triple- Pump  Gear,  the 127* 


Zeuner,  Dr. 


CLASSIFIED    CATALOGUE    OF 

BOOKS  ON  STEAM,  STEAM  ENGINES,  Etc. 

FOR    SALE    BY 

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Barr.  Practical  Treatise  on  High  Pressure  Steam  Boilers,  including 
Results  of  Recent  Experimental  Tests  of  Boiler  Material,  etc.  8vo.  Illus- 
trated. Indianapolis,  1893.  $3.00 

Barrus.  Boiler  Tests  :  Embracing  the  results  of  one  hundred  and  thirty- 
seven  evaporative  tests,  made  on  seventy-one  boilers,  conducted  by  the 
author.  8vo.  New  York,  1900.  $3.00 

Christie.  Chimney  Design  and  Theory.  A  book  for  Engineers  and  Archi- 
tects, containing  all  data  relative  to  Chimney  Designing.  Illustrated 
with  numerous  diagrams  and  half-tone  cuts  of  many  famous  chim- 
neys. 8vo,  cloth.  Illustrated.  New  York,  1899.  $3.00 

Courtney.  The  Boiler  Maker's  Assistant  in  Drawing,  Templating,  and 
Calculating  Boiler  Work  and  Tank  Work,  with  rules  for  the  Evapora- 
tive Power  and  the  Horse  Power  of  Steam  Boilers,  and  the  Proportions 
of  Safety  Valves,  and  Useful  Tables  of  Rivet  Joints  of  Circles,  Weights 
of  Metals,  etc.  Revised  and  edited  by  D.  K.  Clark,  C.E.  Illustrated. 
London,  1901.  (Weale's  Series.)  $0.80 

The  Boiler  Maker's  Ready  Reckoner.  With  examples  of  Practical 
Geometry  and  Templating,  for  the  Use  of  Platers'  Smiths,  and 
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plates  of  famous  chimneys.  2d  edition,  revised.  8vo,  cloth.  $3.00 

Foley,  Nelson.  The  Mechanical  Engineer's  Reference  Book  for  Ma- 
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gineering Data.  Part  II.,  Boiler  Construction.  With  51  Plates  anq 
numerous  illustrations  specially  drawn  for  this  work.  Folio,  half  mor. 
London,  1895.  $25.00 

Horner.  Plating  and  Boiler  Making.  A  Practical  Handbook  for  Work- 
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Hutton.  Steam  Boiler  Construction:  A  Practical  Handbook  for  Engi- 
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tions. 3d  edition.  8vo.  London,  1898.  $6.00 

Munro.  Steam  Boilers :  Their  Defects,  Management,  and  Construction. 
3d  edition  enlarged,  with  numerous  illustrations  and  tables.  i2mo. 
London,  1889.  $1.50 

Roper.  The  Steam  Boiler:  Its  Care  and  Management.  With  instruc- 
tions for  increasing  the  Efficiency  and  Economy,  and  insuring  the  Dura- 
bility and  Longevity  of  all  classes  of  Steam  Boilers,  Stationary,  Loco- 
motive, Marine,  and  Portable.  With  Hints  and  Suggestions  and  Advice 
to  Engineers,  Firemen,  and  Owners  of  Steam  Boilers.  4th  edition, 
revised.  I2mo,  tuck,  mor.  Philadelphia,  1897.  $2.00 

Use  and  Abuse  of  the  Steam  Boiler.  Illustrated.  i2th  edition. 

I2mo,  mor.  tucks.  Philadelphia,  1897.  $2.00 

Rose.  Steam  Boilers.  A  Practical  Treatise  on  Boiler  Construction  and 
Examination.  For  the  Use  of  Practical  Boiler  Makers,  Boiler  Users, 
and  Inspectors,  and  embracing  in  plain  figures  all  the  calculations  neces- 
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Philadelphia,  1897.  $2-5o 

Rowan.  On  Boiler  Incrustation  and  Corrosion.  New  edition,  revised 
and  enlarged  by  F.  E.  Idell.  i6mo,  boards.  New  York,  1895.  $0.50 

Sexton.  Pocket  Book  for  Boiler  Makers  and  Steam  Users,  comprising  a 
variety  of  useful  information  for  Employer  and  Workman,  Government 
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Thurston.  Manual  of  Steam  Boilers :  Their  Designs,  Construction, 
and  Operation.  For  Technical  Schools  and  Engineers.  183  engrav- 
ings in  text.  7th  edition.  8vo.  New  York,  1901.  $5-oo 

A  Handbook  of  Engine  and  Boiler  Trials,  and  of  the  Indicator 

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revised.     Illustrated.     8vo.     New  York,  1897.  $5.00 

Watson,  E.'P.  Small  Engines  and  Boilers.  A  Manual  of  Concise 
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Triplex.  Marine  Boilers.  A  Treatise  on  the  Causes  and  Prevention  of 
their  Priming,  with  Remarks  on  their  General  Management.  Illustrated, 
I2mo.  Sunderland,  1899.  $2.00 

Watson.  Small  Engines  and  Boilers.  A  Manual  of  Concise  and 
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Wilson.  A  Treatise  on  Steam  Boilers:  Their  Strength,  Construction, 
and  Economical  Working.  Enlarged  and  illustrated  from  the  Fifth  Eng- 
lish edition  by  J.  T.  Flather.  i2mo.  New  York,  1897.  $2.50 

• Boiler  and  Factory  Chimneys  :  Their  Draught  Power  and  Stability. 

4th  edition,  I2mo.  London,  1899.  $i.5° 

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Barr.  A  Catechism  on  the  Combustion  of  Coal  and  the  Prevention 
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interested  in  Fuel  Economy,  and  the  Suppression  of  Smoke  from 
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of  Fuel.  With  extensive  additions  in  recent  practice  in  the  Combustion 
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edition.  I2mo.  London,  1891.  $1.50 

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Phillips.  Fuels :  Solid,  Liquid,  and  Gaseous  ;  their  Analysis  and  Valua- 
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Sexton,  A.  H.  Fuels  and  Refractory  Materials.  Svo.  Cloth.  London, 
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Williams.  Fuel  :  Its  Combustion  and  Economy.  Consisting  of  an 
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The  Gas  Engine.  History  and  Practical  Working.  With  100  illus- 
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Donkin.  A  Text-Book  on  Gas,  Oil,  and  Air  Engines  :  or  Internal  Com- 
bustion Motors  without  Boiler.  154  illustrations.  3d  edition,  re- 
vised and  largely  rewritten.  Svo.  London,  1900.  $7.00 

Goodeve.  On  Gas  Engines :  with  Appendix  describing  a  Recent  Engine 
with  Tube  Igniter.  I2mo.  London,  1887.  $1.00 

Hiscox,  Gardner  D.  Gas,  Gasoline  and  Oil  Vapor  Engines.  Their 
Theory  and  Power.  3d  edition,  revised  and  enlarged.  Svo.  cloth. 
Illustrated.  New  York,  1900.  $2.50 

Lockert,  Louis.     Petroleum  Motor-Cars.     i2mo,  cloth.  $1.50 

HEAT.— THERMODYNAMICS. 

Anderson.  On  the  Conversion  of  Heat  into  Work.  A  Practical  Hand- 
book on  Heat  Engines.  4th  edition.  Illustrated.  I2mo.  London, 
1901.  $2.25 

Box.  Treatise  on  Heat  as  Applied  to  the  Useful  Arts,  for  the  use  of 
Engineers,  Architects,  etc.  8th  edition.  I2mo.  London,  1895.  $5.00 

McCulloch.  Elementary  Treatise  on  the  Mechanical  Theory  of  Heat  and 
its  application  to  Air  and  Steam  Engine.  ~8vo.  New  York,  1876.  $3.50 

Maxwell.  Theory  of  Heat.  New  edition,  with  Corrections  and  Addi- 
tions by  Lord  Rayleigh,  Sec.  R.  S.  Illustrated.  I2mo.  New  York, 
1897.  $1.50 

Peabody.  Thermodynamics  of  the  Steam  Engine  and  other  Heat  En- 
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Rontgen.  The  Principles  of  Thermodynamics.  With  special  Applica- 
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sors Verdet,  Zeuner,  and  Pernolet.  Translated,  newly  and  thoroughly 
revised  and  enlarged  by  Professor  A.  Jay  Du  Bois.  732  pages.  3d  edi- 
tion. Svo.  New  York,  1896.  $5.00 


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Tyndall.     Heat  considered   as  a  -mode  of  Motion.     6th  edition.     i2mo. 

New  York,  1890.  $2.50 

Williams.     On  Heat  and  Steam  :  embracing  New  Views  of  Evaporization, 

Condensation,  and  Expansion.     Illus.     8vo.     Philadelphia,  1882.     $2.50 

HOISTING   MACHINERY. 

Colyer.  Hydraulic,  Steam  and  Hand  Power-Lifting  and  Pressing  Ma- 
chinery. 72  large  plates.  8vo.  London,  1892.  $10.00 

Glynn.  Treatise  on  the  Construction  of  Cranes  and  other  Hoisting  Ma- 
chinery. ;th  edition.  Illustrated.  London,  1887.  $0.60 

Marks.  Notes  on  the  Construction  of  Cranes  and  Lifting  Machinery. 
I2mo.  London,  1899.  New  and  enlarged  edition.  net,  1.50 

Towne.  A  Treatise  on  Cranes,  descriptive  particularly  of  those  designed 
and  built  by  the  Yale  and  Towne  Manufacturing  Company,  owning  and 
operating  the  Western  Crane  Company  ,  including  also  a  description  of 
light  hoisting  machinery  as  built  by  the  same  makers.  Svo.  New  York, 
1883.  $1.00 

Weisbach  and  Hermann.  The  Mechanics  of  Hoisting  Machinery,  in- 
cluding Accumulators,  Excavators,  and  Pile-drivers.  A  Text-book  for 
Technical  Schools  and  a  guide  for  Practical  Engineers.  Authorized  trans- 
lation from  the  second  German  edition  by  Karl  P.  Dahlstrom.  177  illus- 
trations. Svo.  New  York,  1893.  $3  75 

ICE-MAKING    MACHINES. 

Dixon.  Manual  of  Ice-Making  and  Refrigerating  Machines.  A  Treatise 
on  the  Theory  and  Practice  of  Cold-Production  by  Mechanical  Means. 
i6mo.  St  Louis,  1894.  $1.00 

Leask.  Refrigerating  Machinery.  Its  Principles  and  Management. 
With  numerous  illustrations.  2d  edition,  revised.  Svo.  London, 

1001.  $2.00 

Ledoux.  Ice-Making  Machines:  the  Theory  of  the  Action  of  the 
Various  Forms  of  Cold-producing  or  so-called  Ice-Machines.  Trans- 
lated from  the  French.  248  pages  and  numerous  Tables.  i6mo. 
New  York,  1897.  $0.50 

Redwood.  Theoretical  and  Practical  Ammonia  Refrigeration.  A  Prac- 
tical Handbook  for  the  use  of  those  in  charge  of  Refrigerating  Plants. 
Illustrated  with  numerous  Tables.  I2mo.  New  York,  1896.  $1.00 

Wallis-Tayler.  Refrigeration  and  Cold  Storage;  being  a  complete 
Practical  Treatise  on  the  Art  and  Science  of  Refrigeration.  Svo, 
cloth.  Illustrated.  net,  $4.50 


LIST  OF  BOOKS. 


INDICATORS. 

Bacon.  Treatise  on  the  Richards  Steam  Engine  Indicator.  With  a 
Supplement,  describing  the  latest  Improvements  in  the  Instruments  for 
Taking,  Measuring,  and  Computing  Diagrams.  Also  an  Appendix,  con- 
taining Useful  Formulas  and  Rules  for  Engineers.  23  diagrams.  4th 
edition.  i6mo,  flex.  New  York,  1883.  $1.00 

Ellison.  Practical  Applications  of  the  Indicator.  With  reference  to  the 
Adjustment  of  Valve  Gear  on  all  Styles  of  Engines.  2d  edition.  8vo. 
100  engravings.  Chicago,  1897.  $2.00 

Hemenway.  Indicator  Practice  and  Steam  Engine  Economy.  With 
Plain  Directions  for  Attaching  the  Indicator,  Taking  Diagrams,  Comput- 
ing the  Horse- Power,  Drawing  the  Theoretical  Curve,  Calculating  Steam 
Consumption,  Determining  Economy,  Locating  Derangement  of  Valves, 
and  making  all  desired  deductions ;  also,  Tables  required  in  making  the 
necessary  computations,  and  an  Outline  of  Current  Practice  in  Testing 
Steam  Engines  and  Boilers.  6th  edition.  I2mo.  New  Vork,  1899. 

#2.00 

Le  Van.  The  Steam  Engine  Indicator  and  its  Use.  A  Guide  to  Practi- 
cal Working  Engineers  for  greater  economy,  and  the  better  Working  of 
Steam  Engines.  i8mo,  boards.  New  York,  1900.  $0.50 

The  Steam  Engine  and  the  Indicator  :  Their  Origin  and  Progressive 

Development,  including  the  most  recent  examples  of  Steam  and  Gas 
Motors,  together  with  the  Indicator,  its  Principles,  its  Utility,  and  its  Ap- 
plication. Illustrated  by  205  engravings,  chiefly  of  Indicator-cards.  8vo. 
Philadelphia,  1890.  $4.00 

Porter.  A  Treatise  on  the  Richards  Steam  Engine  Indicator,  and  the 
Development  and  Application  of  Force  in  the  Steam  Engine.  5th  edi- 
tion, revised  and  enlarged.  8vo.  London,  1894.  $3.00 

Pray.  Twenty  Years  with  the  Indicator.  Being  a  Practical  Text-book 
for  the  Engineer  or  the  Student,  with  no  Complex  Formulae.  With 
many  illustrations  and  rules  as  to  the  best  way  to  run  any  Steam  Engine 
to  get  the  most  economical  results.  How  to  Adjust  Valves  and  Valve 
Motions  Correctly.  Full  directions  for  working  out  Horse-Power,  the 
Amount  of  Steam  or  Water  per  Horse-Power,  Economy  and  Fuel.  Ex- 
tended directions  for  Attaching  the  Indicator,  what  Motions  to  use  and 
those  not  to  use.  Full  directions  for  Computation  of  Power  by  Planim- 
eter  and  other  methods,  with  many  tables  and  hints.  8vo.  New  York, 
1896.  #2.50 


£>.    VAN  NOSTRAATD   COMPANY. 


INJECTORS. 

Kneass.  Practice  and  Theory  of  the  Injector.  8vo.  New  York,  1898. 

$1.50 
Nissenson.  Practical  Treatise  on  Injectors  as  Feeders  of  Steam  Boilers. 

Illustrated.  8vo,  paper.  New  York,  1890.  $0.50 

Pochet.  Steam  Injectors  :  Their  Theory  and  Use.  i6mo,  boards.  New 

York,  1890.  $0.50 

INSTRUCTIONS   TO   ENGINEERS,    FIREMEN, 
AND    BOILER  ATTENDANTS. 

Bale.  A  Hand-Book  for  Steam  Users,  being  Rules  for  Engine  Drivers 
and  Boiler  Attendants,  with  Notes  on  Steam  Engine  and  Boiler  Manage- 
ment and  Steam  Boiler  Explosions.  I2mo.  London,  1890.  $0.80 

Edwards,  goo  Examination  Questions  and  Answers  for  Engineers  and 
Firemen  (Stationary  and  Marine),  who  desire  to  obtain  a  U.  S.  Govern- 
ment or  State  License.  A  new,  revised,  and  enlarged  edition.  321110, 
rnor.  Philadelphia,  1901,  $1.50 

Grimshaw.  Steam  Engino  Catechism.  A  Series  of  Direct  Practical 
Answers  to  Direct  Practical  Questions.  Mainly  intended  for  Young  En- 
gineers. iSmo.  New  York,  1897.  $2.00 

Grimshaw.  The  Engine  Runner's  Catechism.  Telling  how  to  Erect, 
Adjust,  and  Run  the  principal  Steam  Engines  in  use  in  the  United  States. 
Illustrated.  iSmo.  New  York,  1898.  $2.00 

Hawkins.  Maxims  and  Instructions  for  the  Boiler  Room.  Useful  to 
Engineers,  Firemen,  and  Mechanics,  relating  to  Steam  Generators,  Pumps, 
Appliances,  Steam  Heating,  Practical  Plumbing,  etc.  184  illustrations. 
8vo.  New  York,  1901.  $2.00 

Aids  to  Engineers'  Examinations.  Prepared  for  Applicants  of  all 

Grades  with  Questions  and  Answers.  A  Summary  of  the  Principles  and 
Practice  of  Steam  Engineering.  I2mo,  leather,  gilt  edge.  New  York, 
1901.  $2.00 

Reynolds.  The  Engineman's  Pocket  Companion  and  Practical  Educator 
for  Engineman,  Boiler  Attendants,  and  Mechanics.  Illustrated.  i6mo, 
4th  edition.  London,  iqoo.  $1.40 

Roper.  Instructions  and  Suggestions  for  Engineers  and  Firemen  who 
wish  to  Procure  a  License,  Certificate,  or  Permit  to  take  charge  of  any 
class  of  Steam  Engines  or  Boilers,  Stationary,  Locomotive,  and  Marine. 
iSmo,  mor.  Philadelphia,  1894.  $2.00 


LIST  OF  BOOKS. 

Rose.  Key  to  Engines  and  Engine-running.  A  Practical  Treatise 
upon  the  Management  of  Steam  Engines  and  Boilers  for  the  use  of 
those  who  desire  to  pass  an  examination  to  take  charge  of  an  engine 
or  boiler.  I2mo,  cloth.  New  York,  1899.  $2.50 

Questions  and  Answers  for  Engineers.  This  little  book  contains  all 

the  questions  that  Engineers  will  be  asked  when  undergoing  an  exami- 
nation for  the  purpose  of  procuring  licenses,  and  they  are  so  plain  that 
any  Engineer  or  Fireman  of  ordinary  intelligence  may  commit  them  to 
memory  in  a  short  time.  6th  edition.  i8mo,  mor.  Philadelphia.  $2.00 

Stephenson.  Illustrated  Practical  Test  Examination  and  Ready  Refer- 
ence Book  for  Stationary,  Locomotive,  and  Marine  Engineers,  Firemen, 
Electricians,  and  Machinists,  to  procure  Steam  Engineer's  license.  i6mo, 
Chicago,  1892.  $1.00 

Stromberg.  Steam  User's  Guide  and  Instructor.  Plain  and  Correct  Ex- 
planations in  regard  to  Engines,  Pumps,  Dynamos,  and  Electricity.  Prac- 
tically, so  that  Engineers,  Machinists,  Firemen,  and  Electricians  of  Lim- 
ited Education  can  understand  and  become  expert  practical  engineers. 
i6mo.  St.  Louis,  I5th  edition.  1900.  f  $2.50 

Watson.  How  to  Run  Engines  and  Boilers.  Practical  Instruction  for 
Young  Engineers  and  Steam  Users.  2d  edition.  Illustrated.  i6mo. 
New  York,  1896.  $1.00 

Zwicker.  Practical  Instructor  in  questions  and  answers  for  Machinists, 
Firemen,  Electricians,  and  Steam  Engineers.  241110.  St.  Louis,  Mo., 
1898.  $o-7S 

LOCOMOTIVE   ENGINEERING. 

Grimshaw.  Locomotive  Catechism.  Containing  nearly  1,300  Questions 
and  Answers  Concerning  Designing  and  Constructing,  Repairing  and 
Running  Various  Kinds  of  Locomotive  Engines.  Intended  as  Exami- 
nation Questions  and  to  Post  and  Remind  the  Engine  Runner,  Fireman, 
or  Learner.  176  illustrations.  I2mo.  New  York,  1898.  $2.00 

Hill.  Progressive  Examinations  of  Locomotive  Engineers  and  Firemen. 
r6mo.  Terre  Haute,  Ind.,  1899.  $0.50 

Meyer.  Modern  Locomotive  Construction.  1,030  illustrations.  4to.  New 
York,  1899.  $10.00 

Phelan.  Air  Brake  Practice,  being  a  description  of  the  construction,  ob- 
jects sought,  and  results  obtained,  by  the  Westinghouse  automatic  air 
brake,  as  well  as  complete  directions  for  operating  it  under  the  many 
diverse  conditions  in  daily  practice.  3  large  folding  plates.  I2mo.  New 
York,  4th  edition.  #1.00 


D.    VAN  NOSTRAND   COMPANY. 

Reagan.  Locomotive  Mechanism  and  Engineering.  i2mo,  with  145  il- 
lustrations. New  York,  1898.  $2.00 

Reynolds.  Locomotive  Engine  Driving.  A  Practical  Manual  for  Engi- 
neers in  charge  of  Locomotive  Engines.  8th  edition,  enlarged.  i2mo. 
London,  1892.  #1.40 

The  Model  Locomotive  Engineer,  Fireman,  and  Engine  Boy :  Com- 
prising a  Historical  Notice  of  the  Pioneer  Locomotive  Engines  and  their 
Inventors.  I2mo.  London,  1895.  $1.80 

Continuous  Railway  Brakes.  A  Practical  Treatise  on  the  several 

Systems  in  use  in  the  United  Kingdom ;  their  Construction  and  Perform- 
ance. Numerous  illustrations  and  tables.  8vo.  London,  1882.  $3.60 

Engine  Driving  Life :  Stirring  Adventures  and  Incidents  in  the  Lives 

of  Locomotive  Engine  Drivers.  2d  edition,  with  additional  chapters. 
I2mo.  London,  1894.  $0.80 

Rogers.     Pocket  Primer  or  Air  Brake  Instruction.    Stiff  paper  cover.  $0.50 

Roper.  Hand-Book  of  the  Locomotive ;  including  the  construction  of 
engines  and  boilers  and  running  of  locomotives,  i^th  edition,  revised. 
I2mo,  mor.  tucks.  Philadelphia,  1897.  $2.50 

Sinclair.  Locomotive-Engine  Running  and  Management.  A  Practical 
Treatise  on  Locomotive  Engines,  showing  their  performance  in  running 
different  kinds  of  trains  with  economy  and  Despatch.  Also,  directions 
regarding  the  care,  management,  and  repairs  of  Locomotives  and  all  their 
connections.  Illustrated  by  numerous  engravings.  2ist  edition,  revised. 
I2rno.  New  York,  1901.  $2.00 

Stretton.  The  Locomotive  Engine  and  its  Development.  A  Popular 
Treatise  on  the  Gradual  Improvements  made  in  Railway  Engines  be- 
tween the  years  1803  and  1892.  Illustrated.  I2mo.  5th  edition.  Lon- 
don, 1896.  $1.50 

Synnestvedt.  Diseases  of  the  Air  Brake  System.  Their  Causes,  Symp- 
toms, and  Cure.  Illustrated.  I2mo.  1894.  $1.00 

Woods.  Compound  Locomotives.  2d  edition,  revised  and  enlarged  by 
D.  L.  Barnes.  8vo.  Illustrated.  Chicago,  1894.  $3-oo 


MACHINE   TOOLS   AND   APPLIANCES. 

Harrison.  The  Mechanic's  Tool  Book,  with  Practical  Rules  and  Sugges- 
tions for  Machinists,  Iron  Workers,  and  others.  I2mo.  New  York, 
1882.  $1.50 


LIST  OF  BOOKS. 

Hasluck.  The  Mechanics'  Work-shop  Handy  Book.  A  "Practical  Man- 
ual on  Mechanical  Manipulation.  Embracing  Information  on  Various 
Handicraf .  Processes,  with  Useful  Notes  and  Miscellaneous  Memoranda. 
I2mo.  London,  1895.  $0.50 

Knight.  Mechanician.  A  Treatise  on  the  Construction  and  Manipulation 
of  Tools,  for  the  Use  and  Instruction  of  Young  Engineers  and  Scientific 
Amateurs.  4th  edition.  4to.  London,  1888.  $7.25 

Lukin.  Young  Mechanic.  Containing  directions  for  the  use  of  all  kinds 
of  Tools  and  for  construction  of  Steam  Engines  and  Mechanical  Models, 
including  the  Art  of  Turning  in  Wood  and  Metal.  Illustrated.  I2mo. 
New  York.  $i-75 

Rose.  Complete  Practical  Machinist.  Embracing  Lathe  Work,  Vise 
Work,  Drills  and  Drilling,  Taps  and  Dies,  Hardening  and  Tempering, 
the  Making  and  Use  of  Tools,  Tool  Grinding,  Marking  out  Work,  etc. 
Illustrated  by  356  engravings.  I9th  edition,  greatly  enlarged.  I2mo. 
Philadelphia,  1901.  £2.50 

Shelley.  Work-shop  Appliances.  Including  descriptions  of  some  of  the 
Gauging  and  Measuring  Instruments,  Hand  Cutting  Tools,  Lathes,  Drill- 
ing, Planing,  and  other  Machine  Tools  used  by  Engineers.  loth  edition, 
with  an  additional  chapter  on  Milling,  by  R.  R.  Lister.  Illustrated. 
I2mo.  London,  1897.  $1-50 

Smith.  Cutting  Tools  worked  by  Hand  and  Machine.  14  plates  and  51 
illustrations.  2d  edition.  i2mo.  London,  1884.  $'-50 

Usher.  Modern  Machinist.  A  Practical  Treatise  on  Modern  Machine 
Shop  Methods,  describing  in  a  comprehensive  manner  the  most  Approved 
Methods,  Processes,  and  Appliances  Employed  in  Present  Practice,  etc. 
257  illustrations.  I2mo.  New  York,  1895.  $2.50 

Watson.  Modern  Practice  of  American  Machinists  and  Engineers.  i2mo. 
Illustrated.  Philadelphia,  1897.  $2.50 

MECHANICAL   DRAWING   AND   MACHINE 
DESIGN. 

Andre.  Draughtsman's  Hand-Book  of  Plan  and  Map  Drawing;  including 
Instructions  for  the  preparation  of  Engineering,  Architectural  and  Me- 
chanical Drawings,  with  numerous  illustrations,  and  colored  examples. 
8vo.  London,  1891.  $3-75 

Appleton's  Cyclopaedia  of  Technical  Drawing.  Embracing  the  Principles 
of  construction  as  applied  to  Practical  Design.  With  numerous  illustra- 
tions of  Topographical,  Mechanical,  Engineering,  Architectural,  Perspec- 
tive, and  Free-hand  Drawing.  8vo,  leather.  New  York,  1896.  $9,00 


D.    VAN  NO  STRAND   COMPANY 

Barber.  Engineers'  Sketch  Book  of  Mechanical  Movements,  Devices, 
Appliances,  Contrivances,  Details  employed  in  the  Design  and  Con- 
struction of  Machinery  for  every  Purpose.  Collected  from  numer- 
ous sources  and  from  actual  work.  Classified  and  arranged  for 
reference.  Nearly  2000  Illustrations.  4th  edition.  8vo.  London, 
1902.  $4.00 

Building  and  Machine  Draughtsman.  A  Practical  Guide  to  the  Pro- 
jection and  Delineation  of  Subjects  met  with  in  the  practice  of  the 
engineer,  machinist,  and  building  constructor,  etc.;  by  practical 
draughtsmen.  I2mo.  London,  1891.  $2.00 

Burns.  Illustrated  Architectural  Engineering  and  Mechanical  Draw- 
ing Book.  For  the  use  of  Schools,  Students,  and  Artisans.  loth 
edition,  revised  and  corrected,  with  additional  sections  on  impor- 
tant departments  of  the  art.  8vo.  284  illustrations.  New  York, 
1893.  $1,00 

Cathcart,  Prof.  Wm.  L.  Machine  Design:  Fastenings,  with  Tables, 
Diagrams  and  Engravings.  Svo,  cloth.  Illustrated.  In  Press. 

Davidson.  Drawing  for  Machinists  and  Engineers.  Comprising  a  com- 
plete course  of  Drawing  adapted  to  the  requirements  of  Millwrights  and 
Engineers ;  also,  course  of  practical  instruction  in  the  coloring  of  me- 
chanical drawings.  4th  edition.  i6mo.  London.  $1-75 

Donaldson.  Drawing  and  Rough  Sketching  for  Marine  Engineers,  with 
Proportions,  Instructions,  Explanations,  and  Examples ;  also  How  to  De- 
sign Engines,  Boilers,  Propellers,  Paddle  Wheels,  Shafts,  Rods,  Valves, 
etc.  6th  edition.  Illustrated.  London,  1899.  $3.00 

Faunce.  Mechanical  Drawing,  prepared  for  the  use  of  the  students  of 
the  Mass.  Institute  of  Technology.  2d  edition,  revised  and  enlarged. 
Illustrated  and  8  plates.  I2mo.  Boston,  1900.  $1.25 

Fox,  Wm.,  and  C.  W.  Thomas,  M.  E.  A  Practical  Course  in  Mechan- 
ical Drawing.  2d  edition,  revised.  i2mo,  cloth,  with  plates.  $1.25 

Halliday.  First  Course  in  Mechanical  Drawing  (Tracing).  Folio, 
paper.  London,  1889.  $0.75 

—  Mechanical  Graphics.  A  Second  Course  in  Mechanical  Draw- 
ing, with  Preface  by  Professor  Perry.  Svo.  London,  1889.  $2.00 

Hulme.  Mathematical  Drawing  Instruments  and  How  to  Use  Them. 
4th  edition.  I2mo.  New  York,  1890.  $1.50 

Klein.  Elements  of  Machine  Design.  Notes  and  Plates,  Svo.  Beth- 
lehem, Pa.,  1892.  $6.00 


LIST  OF  BOOKS 

Low  and  Bevis.     Manual  of  Machine  Drawing  and  Design.    30!  edition, 
753  illustrations.     8vo.     London,    1901  $2  50 

MacCord.  Practical  Hints  for  Draughtsmen.  Illustrated  with  68  dia- 
grams and  full  page  plates.  3d  edition,  410.  New  York,  1890.  $2.50 
—  Kinematics,  or  Practical  Mechanics.  A  Treatise  on  the  Transmis- 
sion and  Modification  of  Motion  and  the  Construction  of  Mechanical 
Movements.  For  the  use  of  Draughtsmen,  Machinists,  and  Students  of 
Mechanical  Engineering,  in  which  the  laws  governing  the  motions  and 
various  parts  of  Mechanics,  as  affected  by  their  forms  and  modes  of  con- 
nection, are  deduced  by  simple  geometrical  reasoning,  and  their  applica- 
tion is  illustrated  by  accurately  constructed  diagrams  of  the  different 
mechanical  combinations  discussed.  4th  edition.  Svo.  New  York. 
1899.  $5.00 

Minifie.  Mechanical  Drawing.  A  Text-Book  of  Geometrical  Drawing, 
for  the  use  of  Mechanics  and  Schools,  in  which  the  Definitions  and  Rule? 
of  Geometry  are  familiarly  explained :  the  Practical  Problems  are  ar- 
ranged  from  the  most  simple  to  the  more  complex,  and  in  their  descrip 
tion  technicalities  are  avoided  as  much  as  possible.  With  illustrations 
for  Drawing  Plans,  Sections,  and  Elevations  of  Buildings  and  Machin- 
ery; an  Introduction  to  Isometrical  Drawing,  and  an  Essay  on  Linear 
Perspective  and  Shadows.  Illustrated  by  over  200  diagrams,  engraved 
on  steel.  With  an  Appendix  on  the  Theory  and  Application  of  Colors. 
Svo.  New  York,  1893.  $4.00 

Geometrical  Drawing.     Abridged  from  the  octavo  edition,  for  the 

use  of  Schools.     Illustrated  with  48  steel  plates,     gth  edition.     Revised 
and  enlarged.     I2mo.     New  York,  1890.  $2.00 

Palmer.    Mechanical  Drawing,  Projection  Drawing,  Geometric  and  Oblique 

Drawing,  Working  Drawings.     A  Condensed  Text  for  Class  Room  use. 

Svo.     Columbus,  O.     1894.  £i.oc 

Reinhardt,  Chas.  W.   Lettering  for  Draftsmen,  Engineers  and  Students. 

A  Practical  System  of  Free-hand  Lettering  for  Working  Drawings. 

nth  thousand.     Oblong,  boards.  $1.00 

The  Technic  of  Mechanical  Drafting.     A  Practical  Guide  to 

neat,  correct  and  legible  Drawing,  containing  many  Illustrations, 
Diagrams  and  full-page  Plates.     410,  cloth.     Illustrated.  $1.00 


D.    VAN  NOSTRAND   COMPANY. 

Ripper.  Machine  Drawing  and  Design  for  Technical  Schools  and  Engi- 
neer Students.  Being  a  complete  course  of  Instruction  in  Engineering 
Drawing,  with  Notes  and  Exercises  on  the  Application  of  Principles  to 
Engine  and  Machine  Design,  and  on  the  Preparation  of  Finished  Col- 
ored Drawings.  Illustrated  by  52  plates  and  numerous  explanatory 
drawings.  8vo.  London,  1897.  $6.00 

Roberts.  Drawing  and  Designing  for  Marine  Engineers.  21  large  fold- 
ing plates  and  many  other  illustrations  throughout  the  text.  8vo.  Lon- 
don, 1898.  $3.00 

Rose.  Mechanical  Drawing  Self-Taught.  Comprising  Instructions  in 
the  Selection  and  Preparation  of  Drawing  Instruments,  Elementary  In- 
struction in  Practical  Mechanical  Drawing,  together  with  Examples  in 
Simple  Geometry  and  Elementary  Mechanism,  including  Screw  Threads, 
Gear  Wheels,  Mechanical  Motions,  Engines  and  Boilers.  Illustrated  by 
330  engravings.  4th  edition,  revised.  8vo.  Philadelphia,  1902.  $4.00 

Shaw.  Mechanical  Integrators.  Including  the  various  Forms  of  Pla- 
nimeters.  iSmo,  boards.  Illustrated.  New  York,  1886.  $0.50 

Smith.  Graphics,  or  the  Art  of  Calculation  by  Drawing  Lines,  applied 
especially  to  Mechanical  Engineering.  Part  I.  Text,  with  Separate  Atlas 
of  Plates  —  Arithmetic,  Algebra,  Trigonometry,  Vector  and  Lecor  Addi- 
tion, Machine  Kinematics,  and  Statics  of  Flat  and  Solid  Structures.  Svo. 
London,  1888.  $5.00 

Stanley.     Descriptive  Treatise  on  Mathematical  Drawing  Instruments, 

their  Construction,  Uses,  Qualities,  Selection,  Preservation,  and  Sugges- 
tions for  Improvements,  with  Hints  upon  Drawing  and  Coloring.  5th 
edition.  I2mo.  London,  1878.  $2.00 

Tomkins.  Principles  of  Machine  Construction ;  being  an  application  of 
Geometrical  Drawing  for  the  Representation  of  Machinery.  Text  121110, 
Plates  4to.  New  York.  #3. 50 

Unwin.  Elements  of  Machine  Design.  Part  I.  General  Principles,  Fas- 
tenings, and  Transmissive  Machinery.  i6th  edition.  I2mo.  London, 
1898.  $2.00 

Part  II.  Chiefly  on  Engine  Details.  I2mo.  I3th  edition,  revised 

and  enlarged.  London,  1901.  $1.5° 

Warren.  Elements  of  Machine  Construction  and  Drawing  :  or,  Machine 
Drawing,  with  some  elements  of  descriptive  and  rational  kinematics. 
2  vols.  Text  and  plates.  Svo.  New  York.  .  $7.50 


LIST  OF  BOOKS. 

MECHANICAL  ENGINEERS'    HAND-BOOKS. 

Adams.  Hand-Book  for  Mechanical  Engineers.  2d  edition.  Revised 
and  enlarged.  I2mo.  London,  1897.  $2.50 

Appleton's  Cyclopaedia  of  Applied  Mechanics  :  a  Dictionary  of  Mechani- 
cal Engineering  and  the  Mechanical  Arts.  Edited  by  Park  Benjamin. 
Nearly  7,000  illustrations.  Revised  and  improved  edition.  2  vols.  8vo, 
leather.  New  York,  1896.  £15.00 

Bale.  Steam  and  Machinery  Management :  A  Guide  to  the  Arrangement 
and  Economical  Management  of  Machinery,  with  Hints  on  Construction 
and  Selection.  Illustrated.  2d  edition.  i2mo.  London,  1890.  (Weale's 
Series.)  $1.00 

Benjamin.  Wrinkles-  and  Recipes.  Compiled  from  the  Scientific  Ameri- 
can. A  collection  of  Practical  Suggestions,  Processes,  and  Directions, 
for  the  Mechanic,  Engineer,  Farmer,  and  Housekeeper.  With  a  Color 
Tempering  Scale  and  numerous  Wood  Engravings.  5th  edition. 
I2mo.  New  York,  1901.  $2.00 

Byrne.  Hand-Book  for  the  Artisan,  Mechanic,  and  Engineer.  Compris 
ing  the  Grinding  and  Sharpening  of  Cutting  Tools,  Abrasive  Processes, 
Lapidary  Work,  Gem  and  Glass  Engraving,  Varnishing  and  Lackering 
Apparatus,  Materials  and  Processes  for  Grinding  and  Polishing,  etc.  8vo. 
Illustrated.  Philadelphia,  1887.  $5.00 

Carpenter.  Text-Book  of  Experimental  Engineering.  For  Engineers  and 
for  Students  in  Engineering  Laboratories.  249  illustrations.  5th  revised 
edition.  8vo.  New  York,  1898.  $6.00 

Chordal.  Extracts  from  Chordal's  Letters.  Comprising  the  choicest 
selections  from  the  Series  of  Articles  which  have  been  appearing  for  the 
past  two  years  in  the  columns  of  the  American  Machinist.  With  over  50 
illustrations.  (  I2mo.  gth  edition.  New  York,  1901.  $2.00 

Clark.  Manual  of  Rules,  Tables  and  Data  for  Mechanical  Engineers, 
based  on  the  most  recent  investigations.  With  numerous  Diagrams. 
7th  edition.  1,012  pages.  London,  1897.  $5.oo 

Half  morocco.  $7. 50 

Mechanical  Engineers'  Pocket-Book  of  Tables,  Formulae,  Rules, 

and  Data.  A  Handy-Book  of  Reference  for  Daily  Use  in  Engineer- 
ing Practice.  i6mo,  mor.  4th  edition.  London,  1899.  $3.00 

Dixon.  The  Machinists'  and  Steam  Engineers'  Practical  Calculator. 
A  Compilation  of  useful  Rules  and  Problems,  arithmetically  solved, 
together  with  general  information  applicable  to  Shop  Tools,  Mill 
Gearing,  Pulleys  and  Shafts,  Steam  Boilers  and  Engines.  Embracing- 
valuable  Tables  and  Instructions  in  Screw  Cutting,  Valve  and  Link 
Motion.  3d  edition.  i6mo,  mor.,  pocket  form.  New  York,  1901.  $1.25 


D.    VAN  NOSTRAND   COMPANY. 

Engineering  Estimates,  Costs,  and  Accounts.  A  Guide  to  Commercial 
Engineering.  With  numerous  Examples  of  Estimates  and  Costs  of  Mill- 
wright Work,  Miscellaneous  Productions,  Steam  Engines  and  Steam 
Boilers,  and  a  Section  on  the  Preparation  of  Costs  Accounts.  By  a  Gen- 
eral Manager.  2d  edition.  8vo,  London,  1896.  $4.80 

General  Machinist,  Being  a  Practical  Introduction  to  the  Leading  Depart- 
ments of  Mechanism  and  Machinery,  the  Communication  of  Motion  or 
the  Transmission  of  Force  by  Belt,  Rope,  Wire  Rope,  and  Pulley  Gearing 
—  Toothed-Wheel  and  Frictional  Gearing  ;  together  with  the  details  of 
the  component  and  essential  parts  of  mechanism — Shafts,  Pedestals, 
Hanger,  Clutches,  etc.,  and  of  the  methods  of  fitting  up  Machines,  Screw 
Bolts,  Riveting,  etc.  By  various  practical  writers  and  machinists.  75 
illustrations  and  4  folding  plates.  8vo.  London,  1891.  $2.00 

Grimshaw.  Hints  to  Power  Users.  Plain,  Practical  Pointers,  free  from 
high  Science,  and  intended  for  the  man  who  pays  the  bills.  I2mo.  New 
York,  1891.  «  $  i.  oo 

Hasluck.  Mechanic's  Workshop  Handy-Book.  A  Practical  Manual  on 
Mechanical  Manipulation.  Embracing  Information  on  Various  Handi- 
craft Processes,  with  Useful  Notes,  and  Miscellaneous  Memoranda. 
I2mo.  London,  1888.  $0.50 

Haswell.  Engineers'  and  Mechanics'  Pocket  Book,  Containing  Weights 
and  Measures,  Rules  of  Arithmetic,  Weights  and  Materials,  Latitude  and 
Longitude,  Cables  and  Anchors,  Specific  Gravities,  Squares,  Cubes,  and 
Roots,  etc. ;  Mensuration  of  Surfaces  and  Solids,  Trigonometry,  Me- 
chanics, Friction,  Aerostatics,  Hydraulics  and  Hydrodynamics,  Dynamics, 
Gravitation,  Animal  Strength,  Windmills,  Strength  of  Materials,  Limes, 
Mortars,  Cements,  etc. ;  Wheels,  Heat,  Water,  Gunnery,  Sewers,  Com- 
bustion, Steam  and  the  Steam  Engine,  Construction  of  Vessels,  Miscel- 
laneous Illustrations,  Dimensions  of  Steamers,  Mills,  etc.;  Orthography 
of  Technical  Words  and  Terms,  etc.  6yth  edition.  Revised  and 
enlarged.  I2mo,  mor.  tuck.  New  York,  1902.  $4.00 

Hawkins.  Hand-Book  of  Calculations,  for  Engineers  and  Firemen  ; 
relating  to  the  Steam  Engine,  the  Steam  Boiler,  Pumps,  Shafting, 
etc.  Illustrated.  8vo.  New  York,  1902.  $2.00 

Button.  Works  Manager's  Hand-Book  of  Modern  Rules,  Tables,  and 
Data  for  Civil  and  Mechanical  Engineers,  Millwrights,  and  Boiler  Makers, 
Tool  Makers,  Machinists,  and  Metal  Workers,  Iron  and  Brass  Founders, 
etc.  5th  edition,  revised,  with  additions.  8vo,  half-bound.  London, 
1895- 


LIST  OF  BOOKS. 

Hutton.  Practical  Engineer's  Hand-Book.  Comprising  a  Treatise  on 
Modern  Engines  and  Boilers,  Marine,  Locomotive,  and  Stationary,  and 
containing  a  large  Collection  of  Rules  and  Practical  Data  Relating  to 
Recent  Practice  in  Designing  and  Constructing  all  kinds  of  Engines, 
Boilers,  and  other  Engineering  Work.  5th  edition,  carefully  revised,  with 
additions.  370  illustrations.  8vo.  London,  1896.  $7«oo 

Kent.  Mechanical  Engineers'  Pocket-Book.  A  Reference  Book  of  Rules, 
Tables,  Data,  and  Formulae,  for  the  Use  of  Engineers,  Mechanics,  and 
Students.  1,087  pages.  5th  edition.  I2mo.  New  York,  1902.  $5.00 

Knight.  American  Mechanical  Dictionary.  A  Descriptive  Word  Book 
of  Tools,  Instruments,  Chemical  and  Mechanical  Processes;  Civil,  Me- 
chanical, Railroad,  Hydraulic,  and  Military  Engineering.  A  History  of 
Inventions.  General  Technological  Vocabulary,  and  Digest  of  Mechani- 
cal Appliances  in  Science  and  the  Industrial  and  Fine  Arts.  3  vols. 
Illustrated,  8vo.  Boston,  1884.  $24.00 

Supplement  to  the  above,  $9.00 

The  4  vols.,  complete,  $-7-S° 

Lockwood's  Dictionary  of  Terms  used  in  the  Practice  of  Mechanical  En- 
gineering. Embracing  those  current  in  the  Drawing  Office,  Pattern  Shop, 
Foundry,  Fitting,  Turning,  Smiths'  and  Boiler  Shops,  etc.,  comprising 
upwards  of  6,000  definitions.  Edited  by  a  Foreman  Pattern  Maker. 
3d  edition.  I2mo.  London,  1902.  $3-°o 

Molesworth.  Pocket-Book  of  Useful  Formulae  and  Memoranda  for 
Civil  and  Mechanical  Engineers.  24th  edition,  revised  and  enlarged. 
Pocket-book  form.  London,  1901.  $2.00 

Moore.  Universal  Assistant  and  Complete  Mechanic  :  Containing  over 
One  Million  Industrial  Facts,  Calculations,  Receipts,  Processes, 
Trade  Secrets,  Rules,  Business  Forms,  Legal  Items,  etc.  Illustrated. 
i2mo.  New  York.  $2.50 

Rankine.  Useful  Rules  and  Tables  relating  to  Mensuration,  Engineering 
Structures,  and  Machines.  7th  edition,  thoroughly  revised  by  W.  J. 
Millar.  With  Electrical  Engineering  Tables,  Tests,  and  Formulae  for  the 
use  of  Engineers,  by  Prof.  A.  Jamieson.  I2mo.  London,  1889.  $4.00 

Roper.  Engineers'  Handy-Book.  Containing  a  full  explanation  of  the 
Steam  Engine  Indicator,  and  the  Use  and  Advantage  to  Engineers  and 
Steam  Users.  With  Formulae  for  estimating  the  Power  of  all  Classes 


D.    VAN  NOSTRAND   COMPANY. 

of  Steam  Engines ;  also  Facts,  Figures,  Questions,  and  Tables,  for  Engi- 
neers who  wish  to  qualify  themselves  for  the  United  States  Navy,  the 
Revenue  Service,  the  Mercantile  Marine,  or  to  take  charge  of  the  better 
class  of  stationary  Steam  Engines.  Illustrated.  isth  edition. 
i6mo,  mor.  tucks.  Philadelphia,  1901.  $3-5o 

Scribner.  Engineers'  and  Mechanics'  Companion.  Comprising  United 
States  Weights  and  Measures,  Mensuration  of  Superfices  and  Solids; 
Tables  of  Squares  and  Cubes ;  Square  and  Cube  Roots ;  Circumference 
and  Areas  of  Circles  ;  the  Mechanical  Powers  ;  Centres  of  Gravity ;  Gravi- 
tation of  Bodies;  Pendulums;  Specific  Gravity  of  Bodies;  Strength, 
Weight,  and  Crush  of  Materials  ;  Water-wheels,  Hydrostatics,  Hydraulics, 
Statics,  Centres  of  Percussion  and  Gyration ;  Friction  Heat ;  Tables  of 
the  Weight  of  Metals,  Scantling,  etc.;  Steam  and  Steam  Engine. 
2ist  edition,  revised.  i6mo,  full  mor.  New  York,  1902.  $1.50 

Spons'  Tables  and  Memoranda  for  Engineers,  and  convenient  refer- 
ence for  the  pocket.  I2th  edition.  641110,  roan,  gilt  edges.  London, 
1901.  In  cloth  case.  $0.50 

Mechanics'  Own  Book.  A  Manual  for  Handicraftsmen  and 

Amateurs.  Complete  in  one  large  vol.,  8vo,  containing  700  pages 
and  1,420  Illustrations.  6th  edition.  London,  1901.  $2.50 

Dictionary  of  Engineering.     Civil,  Mechanical,  Military,  and  Naval, 

with  Technical  Terms  in  French,  German,  Italian,  and  Spanish.     8  vols. 

8vo,  cl.     London,  1874.  Each,  $5.00 

—  Supplement  to  above.     3  vols.,  cl.     London,  1881.  Each,  $5.00 


Templeton.  Practical  Mechanics'  Workshop  Companion.  Completing 
a  great  variety  of  the  most  useful  Rules  and  Formulas  in  Mechanical 
Science,  with  numerous  Tables  of  Practical  Data  and  Calculated  Results 
for  Facilitating  Mechanical  Operations.  i8th  edition,  revised,  mod- 
ernized, and  considerably  enlarged,  by  Walter  S.  Hutton.  i6mo, 
leather.  London,  1902.  $2.00 

Engineers',  Millwrights',  and  Mechanics'  Pocket  Companion. 

Comprising  Decimal  Arithmetic,  Tables  of  Square  and  Cube  Roots,  Prac- 
tical Geometry,  Mensuration,  Strength  of  Materials,  Mechanical  Powers, 
Water  Wheels,  Pumps  and  Pumping  Engines,  Steam  Engines,  Tables  of 
Specific  Gravity,  etc.  Revised,  corrected,  and  enlarged  from  the  8th  Eng- 
lish edition,  and  adapted  to  American  Practice,  with  the  addition  of  much 
new  matter.  Illustrated  by  J.  W.  Adams.  12 mo,  mor.  tucks.  New  York, 

1893.  .          #2.00 


LIST  OF  BOOKS. 

Van  Cleve.  English  and  American  Mechanic.  An  every-day  Hand-Book 
for  the  Workshop  and  the  Factory.  Containing  Several  Thousand  Re- 
ceipts, Rules,  and  Tables  indispensable  to  the  Mechanic,  the  Artisan,  and 
the  Manufacturer.  A  new,  revised,  enlarged,  and  improved  edition. 
Edited  by  Emory  Edwards,  M.E.  I2mo.  Philadelphia,  1893.  $2.00 

MECHANICS  (ELEMENTARY  AND  APPLIED). 

Church.     Notes  and  Examples  in  Mechanics  ;  with  an  Appendix  on  the 

Graphical  Statics  of  Mechanism.     128  illustrations  and  6  plates.     8vo. 

2d  edition,     New  York,  1900.  $2.00 

Cotterill.     Applied   Mechanics,  an  Elementary  General  Introduction    to 

the  Theory  of  Structures  and  Machines.     Illustrated,     jd  edition.     8vo. 

London,  1895.  $5.00 

—  and  Slade.     Lessons  in  Applied  Mechanics.     i2mo.    London,  1894. 

Net  $1.25 

Dana.     A  Text-Book  of  Elementary  Mechanics  for  the  use  of  Colleges 

and  Schools.     I2th  edition.     I2mo.     New  York,  1901.  $1-50 

DuBois.  Elementary  Principles  of  Mechanics.  Designed  as  a  Text-Book 
for  technical  schools.  3  vols.  Svo.  New  York. 

Vol.  I.     Kinematics.  $3.50 

Vol.  II.     Statics.  $4-00 

Vol.  III.     Kinetics.  $3-5° 

Garnett.  Treatise  on  Elementary  Dynamics.  For  the  use  of  Colleges 
and  Schools.  5th  edition.  Svo.  London,  1889.  Net  $\.$o 

Geldard.     Statics   and   Dynamics.     Illus.    i2mo.    London,  1893.     $1.50 

Goodeve.  Principles  of  Mechanics.  New  edition,  rewritten  and  enlarged. 
I2mo.  London,  1889.  $2.50 

Manual  of  Mechanics.     An  Elementary  Text-Book  for  Students  of 

Applied  Mechanics.     Illustrated.     I2mo.     London,  1881.     .  $0.80 

Hancock.  Text-Book  of  Mechanics  and  Hydrostatics.  With  over  500 
diagrams.  Svo.  New  York,  1894.  #!-75 

Hughes.  Condensed  Mechanics  :  a  selection  of  Formulae,  Rules,  Tables, 
and  Data  for  the  Use  of  Engineering  Students,  Science  Classes,  etc.,  in 
accordance  with  the  requirements  of  the  Science  and  Art  Department. 
I2mo.  London,  1891.  $1.00 

Jamieson.  Elementary  Manual  of  Applied  Mechanics.  Specially  ar- 
ranged for  the  use  of  First  Year  Science  and  Art,  City  and  Guilds  of 
London  Institute,  and  other  Elementary  Engineering  Students. 
4th  edition,  revised  and  enlarged.  I2mo.  London,  1900.  $i.2S 


D.    VAN  NOSTRAND   COMPANY. 

Kennedy.     Mechanics  of  Machinery.    With  numerous  illustrations,    izmo; 

London,  1886.  $3-5O 
Kinematics  of  Machinery;  or,  The  Elements  of  Mechanism.  i6mo, 

boards.  New  York,  iSSi.  .'*  #0.50 

Nystrom.  New  Treatise  on  Elements  of  Mechanics.  8vo.  Philadelphia, 

1875.  $2.00 

Perry.  Applied  Mechanics.  *  Illustrated.  i2mo.  London,  igoi. 

$2.50 

Practical  Mechanics.  Being  the  Fourth  Volume  of  «  Amateur  Work  Il- 
lustrated." Plates  and  illustrations.  4to.  London.  $3.00 

Rankine.  Applied  Mechanics,  comprising  Principles  of  Statics,  Cinemat- 
ics, and  Dynamics,  and  Theory  of  Structures,  Mechanism,  and  Machines. 
I2mo.  i6th  edition,  thoroughly  revised,  by  W.  J.  Millard.  Lon- 
don, 1901.  $5-oo 

—  and  Bamber.  Mechanical  Text-Book  ;  or,  Introduction  to  the 
Study  of  Mechanics  and  Engineering.  With  numerous  Diagrams. 
4th  edition,  revised.  8vo.  London,  1890.  $3.50 

Stahl  and  Woods.  Elementary  Mechanism.  A  Text-Book  for  Stu- 
dents of  Mechanical  Engineering,  nth  edition,  revised  and  en- 
larged. Illustrated.  I2mo.  New  York,  1901.  $2.00 

Weisbach.  Theoretical  Mechanics,  with  an  Introduction  to  the.  Cal- 
culus. Translated  from  the  4th  German  edition  by  E.  B.  Coxe. 
9th  edition,  revised.  8vo,  cloth.  New  York,  1899.  $6.00 

Sheep.  $7.00 

Vol.  II.,  Part  i.  Hydraulics  and  Hydraulic  Motors.  $5-OO 

Vol.  II.,  Part  2.  Heat,  Steam,  and  Steam  Engines.  $5.00 

Vol.  III.,  Part  i.  Kinematics  and  Machinery  of  Transmission.  $5.00 
Vol.  III.,  Part  2.  Machinery  of  Transmission  and  Governors.  $5-OO 

Wood.  Elements  of  Analytical  Mechanics.  With  numerous  examples 
and  illustrations.  For  use  in  Scientific  Schools  and  Colleges.  7th  edi- 
tion, revised  and  enlarged,  comprising  Mechanics  of  Solids  and  Mechanics 
of  Fluids,  of  which  Mechanics  of  Thirds  is  entirely  new.  8vo.  New 
York,  1900.  $3-°° 

Principles  of  Elementary  Mechanics.  Fully  illustrated.  Qth  edition. 

1 2  mo.  New  York,  1894.  $1.25 

Wright.  Text-Book  of  Mechanics.  With  numerous  examples.  3d  edi 
tion.  I2mo,  New  York.  $2.50 


LIST  OF  BOOKS. 


MISCELLANEOUS. 

Amateur  Mechanic's  Workshop.  A  Treatise  containing  plain  and  concise 
directions  for  the  manipulation  of  Wood  and  Metals,  including  Casting, 
Forging,  Brazing,  Soldering,  and  Carpentry.  By  the  author  of  "  The 
Lathe  and  its  Uses."  7th  ed.  Illustrated.  Svo.  London,  1888.  $3,00 

Hiscox,  Gardner  D.  Compressed  Air;  Its  Production,  Uses,  and  Appli- 
cations. Comprising  the  Physical  Properties  of  Air  from  a  Vacuum 
to  its  Liquid  State,  its  Thermodynamics,  Compression,  Transmis- 
sion, and  Uses  as  a  Motive  Power.  With  40  Air  Tables  and  545 
Illustrations.  Svo,  cloth.  New  York,  1901.  $5.oo 

Half  morocco.  $6.50 

Plympton,  Prof.  Geo.  W.  How  to  become  an  Engineer ;  or,  the  Theo- 
retical and  Practical  Training  necessary  in  fitting  for  the  Duties  of 
the  Civil  Engineer.  (Van  Nostrand's  Science  Series).  $0.50 

STEAM   AND    STEAM    ENGINES. 

Alexander.  Model  Engine  Construction.  With  Practical  Instructions  to 
Artificers  and  Amateurs.  Containing  numerous  illustrations  and  twentyr 
one  Working  Drawings,  from  Original  Drawings  by  the  Author.  i2mo. 
London,  1895.  $3.00 

Baker.  Treatise  on  the  Mathematical  Theory  of  the  Steam  Engine. 
With  Rules  at  length  and  Examples  worked  out,  for  the  use  of  practical 
men,  with  numerous  diagrams.  8th  edition.  London,  1890.  $0.60 

Bale.  How  to  Manage  a  Steam  Engine  ;  a  Handbook  for  all  who  use 
Steam.  Illustrated,  with  examples  cf  different  Types  of  Engines  and 
Boilers ;  with  Hints  on  their  Construction,  Working,  Fixing,  Economy 
of  Fuel,  etc.  7th  edition.  I2mo.  London,  1890.  $0.80 

Barms,  Geo.  H.,  S.B.  Engine  Tests;  embracing  the  results  of  over 
100  Feed- Water  Tests  and  other  investigations  of  various  kinds  of 
Steam  Engines,  conducted  by  the  author.  Illustrated.  Svo,  cloth. 
New  York,  1900.  $4.00 

Bourne.  Catechism  of  the  Steam  Engine  in  its  various  Applications  to 
Mines,  Mills,  etc.  New  edition,  enlarged.  Illustrated.  i2mo.  New 
York,  1897.  $2.oc 

-  Hand-Book  of  the  Steam  Engine,  containing  all  the  Rules  required 
for  the  right  Construction  and  Management  of  Engines  of  every  Class. 
with  the  easy  Arithmetical  Solution  of  those  Rules.  Illustrated.  I2mo 
New  York,  1892.  $1.7* 

Burn.  Steam  Engine,  its  History  and  Mechanism.  3d  edition.  Svo, 
Illustrated.  London,  1857.  fa.w. 


D.    VAN  NOSTRAND   COMPANY. 

Clark.  Steam  and  the  Steam  Engine,  Stationary  and  Portable.  (Being 
an  Extension  of  the  Elementary  Treatise  on  the  Steam  Engine,  of  Mr. 
John  Sewell.)  4th  edition.  London,  1892.  $1.40 

The  Steam  Engine.     A  Treatise  on  Steam  Engines   and  Boilers ; 

comprising  the  Principles  and  Practice  of  the  Combustion  of  Fuel,  the 
Economical  Generation  of  Steam,  the  Construction  of  Steam  Boilers, 
and  the  principles,  construction,  and  performance  of  Steam  Engines, 
Stationary,  Portable,  Locomotive,  and  Marine,  exemplified  in  Engines 
and  Boilers  of  recent  date.  Illustrated  by  above  1,300  figures  in  the  text, 
and  a  series  of  folding  plates  drawn  to  scale.  2  vols.  8vo.  London, 
1895.  $15.00 

Colyer.  Treatise  on  Modern  Steam  Engines  and  Boilers,  including  Land, 
Locomotive,  and  Marine  Engines  and  Boilers.  For  the  use  of  Students. 
With  46  plates.  4to.  London,  1886.  $5.00 

Cotterill.  Steam  Engine  considered  as  a  Thermodynamic  Machine.  A 
Treatise  on  the  Thermodynamic  Efficiency  of  Steam  Engines.  Illus- 
trated by  tables,  diagrams,  and  examples  from  practice.  3d  edition,  re- 
vised and  enlarged.  8vo.  London.  1896.  net  $4.50 

Diesel.  Theory  and  Construction  of  a  Rational  Heat  Motor.  Translated 
from  the  German  by  Bryan  Donkin.  With  eleven  figures  in  the  text  and 
three  plates.  8vo.  London,  1894.  $2.50 

Edwards.  American  Steam  Engineer,  Theoretical  and  Practical.  With 
Examples  of  the  latest  and  most  approved  American  Practice  on  the  De- 
sign and  Construction  of  Steam  Engines  and  Boilers  of  every  description. 
For  the  use  of  Engineers,  Machinists,  Boiler  Makers,  etc.  Illustrated  by 
77  engravings.  I2mo.  Philadelphia,  1897.  $2.50. 

. Practical  Steam  Engineers'  Guide  in  the  Design,  Construction,  and 

Management  of  American  Stationary,  Portable,  and  Steam  Fire  Engines, 
Steam  Pumps,  Boilers,  Injectors,  Governors,.  Indicators,  Pistons,  and 
Rings,  Safety  Valves  and  Steam  Gauges.  For  the  use  of  Engineers, 
Firemen,  and  Steam  Users.  Illustrated.  3d  edition,  revised  and  cor 
rected.  i2mo.  Philadelphia,  1900.  $2.50 

Evers.  Steam  and  other  Prime  Movers.  A  Text-Book  both  Theoretical 
and  Practical.  Illustrated.  I2mo.  London,  1890.  $i-5° 

. Steam  and  the  Steam  Engine  ;  Land,  Marine,  and  Locomotive      II 

lustrated.     i2mo.     New  York.  $1.00 

Ewing.  Steam  Engine  and  other  Heating  Engines.  Illustrated.  8vo. 
Cambridge,  1899.  #3-75 


LIST  OF  BOOKS. 

Goodeve.  Text-Book  on  the  Steam  Engine.  With  a  Supplement  on  Gas 
Engines  and  on  Heat  Engines.  I3th  edition,  enlarged.  I2mo.  143 
illustrations.  London,  1896.  §2.00 

Gould.     Arithmetic  of  the  Steam  Engine.     i2mo.     N.  Y.     1898.     £1.00 

Grimshaw.  Steam  Engine  Catechism.  A  series  of  direct  practical  an 
swers  to  direct  practical  questions,  mainly  intended  for  young  engineers 
and  for  examination  questions,  nth  edition,  enlarged  and  improved. 
i8mo.  New  York,  1897.  52. oo 

Haeder.  Hand-Book  on  the  Steam  Engine  with  especial  Reference  to 
Small  and  Medium  sized  Engines.  For  the  Use  of  Engine  Makers,  Me- 
chanical Draughtsmen,  Engineering  Students,  and  Users  of  Steam 
Power.  1,100  illustrations.  i2mo.  London,  1896.  ^3.00 

Henthorn.  Corliss  Engine  and  its  Management.  Edited  by  E.  P.  Watson, 
jd  edition,  enlarged  with  an  appendix,  by  Emil  Herter.  Illustrated. 
i8mo.  New  York,  1897.  $1.00 

Holmes.  Steam  Engine.  21 2  illustrations.  loth  edition.  i2mo.  London, 
1900.  £2.00 

This  is  a  complete  practical  and  theoretical  treatise  on  the  steam-engine,  written  in 
very  clear  and  beautiful  style,  rendering  the  more  abstruse  principles  of  the  subject  as 
plain  and  simple  as  it  is  probably  possible  to  make  them.  It  is  one  of  the  best,  if  not  the 
best,  combinations  of  theoretical  investigation  and  practical  applications  in  the  whole  lite- 
rature of  the  subject,  and  forms  an  admirable  companion  to  Ripper's  smaller  and  more 
exclusively  practical  treatise. 

Jamieson.  Text-Book  of  Steam  and  Steam  Engines.  i3th  edition, 
with  numerous  Diagrams,  four  folding  Plates,  and  Examination 
Questions.  I2tno.  London,  1901.  $3.00 

-  Elementary  Manual  on  Steam  and  the  Steam  Engine.  With 
numerous  Diagrams,  Arithmetical  Examples,  and  Examination 
Questions.  8th  edition.  I2mo.  London,  1900.  $1.40 

Lardner.  Treatise  on  the  Steam  Engine,  for  the  Use  of  Beginners. 
i6th  edition.  Illustrated.  London,  1893.  $0.60. 

Le  Van.  Steam  Engine  and  the  Indicator;  their  Origin  and  Progres- 
sive Development,  including  the  most  recent  examples  of  Steam 
and  Gas  Motors,  together  with  the  Indicator,  its  Principles,  its 
Utility,  and  its  Application.  Illustrated  by  205  Engravings,  chiefly 
of  Indicator  Cards.  Svo.  Philadelphia,  1900.  $4.00 

Mallet.     Compound  Engines.    i6mo,  boards.    New  York,  1884.     $0.50 

Marks.  Relative  Proportions  of  the  Steam  Engine.  Illustrated.  3d  edi- 
tion. I2mo.  Philadelphia,  1896.  $3.00 

Peabody.  Table  of  the  Properties  of  Saturated  Steam  and  other 
Vapors.  6th  edition.  8vo.  New  York,  1901.  $1.00 


D.    VAN  NOSTRAND   COMPANY, 

;• 

Pray.  Steam  Tables  and  Engine  Constants.  For  facilitating  all  calcu- 
lations upon  Indicator  Diagrams  or  Various  Problems  connected  with 
the  operation  of  the  Steam  Engine,  from  reliable  data  and  with  precision 
compiled  from  Regnault,  Rankine,  and  Dixon  directly,  making  use  of  the 
exact  records.  8vo.  New  York,  1894.  $2.00 

Rankine.  Manual  of  the  Steam  Engine  and  other  Prime  Movers,  with 
numerous  tables  and  illustrations.  I2moi  I4th  edition.  London,  1897. 

$5.00 

Rigg.  Practical  Treatise  on  the  Steam  Engine,  containing  Plans  and 
Arrangements  of  Details  for  Fixed  Steam  Engines,  with  Essays  on  the 
Principles  involved  in  D,esign  and  Construction.  Copiously  illustrated 
with  woodcuts  and  96  plates.  4to.  2d  edition.  New  York,  1894. 

$10.00 

Ripper.     Steam.      Illustrated.     i2mo.     London,  1889.  $1.00 

This  work  is  based  upon  a  course  of  lectures  given  to  an  evening  class  of  young  me- 
chanical engineers  on  steam,  steam-engines,  and  boilers.  It  is  remarkably  clear,  concise, 
and  practical ;  no  superfluous  matter  is  introduced,  and  every  page  goes  directly  to  the 
point.  It  is  the  best  book  for  beginners,  and  also  for  those  who  wish  to  have  a  manual 
embracing  the  practical  features  of  the  subjects  in  small  compass. 

Roper.  Hand-Book  of  Modern  Steam  Fire  Engines ;  including  the  run- 
ning, care,  and  management  of  Steam  Fire  Engines  and  Fire  Pumps. 
2d  edition,  revised  and  corrected  by  H.  L.  Stellwagen.  Illustrated. 
I2mo,  mor.  tucks.  Philadelphia,  1897.  $3-5° 

Hand-Book  of  Land  and  Marine  Engines,  including  the  Modelling, 

Construction,  Running,  and  Management  of  Land  and  Marine  Engines 

and  Boilers,     gth  edition,  revised,  enlarged,  and  improved.     i2mo,  mor. 

•  tucks.     Philadelphia,  1897.  #3-5° 

. Catechism  of  High  Pressure  or  Non-Condensing  Steam  Engines, 

including  the  Modelling,  Constructing,  Running,  and  Management  of 
Steam  Engines  and  Steam  Boilers.  2oth  edition,  revised  and  enlarged. 
Illustrated.  i2mo,  mor.  tucks.  Philadelphia,  1897.  $2.00 

Young  Engineer's  Own  Book.  Containing  an  Explanation  of  the 

Principle  and  Theories  on  which  the  Steam  Engine  as  a  Prime  Mover  is 
based,  with  a  description  of  different  kinds  of  Steam  Engines,  Condens- 
ing and  Non -Condensing,  Marine,  Stationary,  Locomotive,  Fire,  Trac- 
tion, and  Portable.  106  illustrations.  3d  edition,  revised.  16  mo,  mor. 
tucks.  Philadelphia,  1897.  $3-°° 

Rose.  Modern  Steam  Engines.  An  Elementary  Treatise  upon  the 
Steam  Engine,  written  in  Plain  Language ;  for  use  in  the  Workshop  as 
well  as  in  the  Drawing  Office.  Giving  Full  Explanations  of  the  Con- 


LIST  OF  BOOKS. 

struction  of  Modern  Steam  Engines;  including  Diagrams  showing  their 
Actual  Operation  ;  together  with  Complete  but  Simple  Explanation  of 
the  Operations  of  various  kinds  of  Valves,  Valve  Motions,  and  Link 
Motions,  etc.,  thereby  enabling  the  ordinary  engineer  to  clearly  under- 
stand the  Principles  involved  in  their  Construction  and  use,  and  to  Plot 
out  their  movements  upon  the  Drawing  Board.  New  edition,  revised 
and  improved.  453  illustrations.  4to.  Philadelphia,  1900.  §6.00 

Key  to  Engines  and  Engine  Running.  A  Practical  Treatise  upon 

the  Management  of  Steam  Engines  and  Boilers,  for  the  use  of  those 
who  desire  to  pass  an  Examination  to  take  Charge  of  an  Engine  or 
Boiler.  With  numerous  Illustrations  and  Instructions  upon  Engineers' 
Calculations,  Indicator  Diagrams,  Engine  Adjustments,  and  other  Valu- 
able Information  necessary  for  Engineers  and  Firemen.  I2mo.  N.  Y. 
1899.  ^2.50 

Thurston.  History  of  the  Growth  of  the  Steam  Engine.  4th  revised 
edition.  Illustrated.  i2mo.  New  York,  1897.  £2.50 

Manual  of  the  Steam  Engine.  For  Engineers  and  Technical 

Schools.  Part  I,  Structure  and  Theory.  Illustrated.  5th  edition, 
revised.  8vo.  New  York,  1900.  $6.00 

Part  II.  Design,  Construction,  and  Operation.  Illustrated,  4th  edi- 
tion, revised.  8vo.  New  York,  1900.  $6.00 
Or  in  sets.  $10.00 

Hand-Book  of  Engine  and  Boiler  Trials,  and  of  the  Indicator 

and  Prony  Brake,  for  Engineers  and  Technical  Schools.  Illustrated. 
4th  and  revised  edition.  8vo.  New  York,  1897.  §5.00 

Stationary  Steam  Engines,  Simple  and  Compound,  especially 

as  adapted  to  Electric  Lighting  Purposes.  5th  edition,  revised,  with 
additions.  Illustrated,  I2mo.  New  York,  1893.  $2.50 

Turnbull.  Treatise  on  the  Compound  Engine.  2d  edition,  revised 
and  enlarged  by  Prof.  S.  W,  Robinson.  i6mo,  boards.  New  York, 
1884.  $0.50 

Watson,  E.  P.  Small  Engines  and  Boilers.  A  manual  of  Concise 
and  Specific  Directions  for  the  Construction  of  Small  Steam  Engines 
and  Boilers  of  Modern  Types  from  five  Horse-power  down  to  model 
sizes.  Illustrated.  I2mo,  cloth.  $1.25 

Weisbach.  Heat,  Steam,  and  Steam  Engine.  Translated  from  the 
4th  edition  of  Vol.  II.  of  Weisbach's  Mechanics.  Containing  Notes 
giving  practical  examples  of  Stationary,  Marine,  and  Locomotive 
Engines,  showing  American  practice,  by  R.  H.  Buel.  Numerous 
illustrations.  8vo.  New  York,  1891.  $5.00 


D.    VAN  NOSTRAND   COMPANY 

Whitham.  Steam  Engine  Design.  For  the  use  of  Mechanical  Engi- 
neers, Students,  and  Draughtsmen.  3d  edition,  revised.  With  210 
illustrations.  8vo.  New  York,  1902.  $5.00 

TRANSMISSION    OF    POWER,    BELTING,    ETC. 

Kerr,  E.  W.,  M.E.  Power,  and  Power  Transmission.  A  Series  of 
Lectures  delivered  to  Students,  on  the  Elementary  Principles  of 
Engineering.  Containing  numerous  full-page  Diagrams,  Figures 
and  Tables.  Illustrated.  8vo,  cloth.  New  York,  1902.  $2.00 

Toothed  Gearing.  A  Practical  Hand-Book  for  Offices  and  Workshops. 
By  a  Foreman  Pattern  Maker.  184  illustrations.  I2mo.  London, 
1892.  $2.50 

Unwin.  On  the  Development  and  Transmission  of  Power  from  Cen- 
tral Stations.  Being  the  Howard  Lectures  delivered  at  the  Society 
of  Arts  in  1893.  Illustrated.  8vo,  New  York,  1894.  $3.50 

VALVES  AND  VALVE  GEARS. 

Auchincloss.  Practical  Application  of  the  Slide-Valve  and  Link- 
Motion  to  Stationary,  Portable,  Locomotive,  and  Marine  Engines, 
with  new  and  simple  methods  for  proportioning  the  parts.  Illus- 
trated. I4th  edition,  revised  and  enlarged.  8vo.  New  York, 
1901.  $2.00 

Bankson.  Slide  Valve  Diagrams.  A  French  Method  of  Obtaining 
Slide  Valve  Diagrams.  8  Plates.  i6mo.  New  York,  1892.  $0.50 

Begtrup,  Julius.  Slide  Valve  and  its  Functions.  With  special  refer- 
ence to  modern  Practice  in  the  United  States.  With  many  Dia- 
grams. Illustrated.  8vo,  cloth.  $2.00 

Buel.  Safety  Valves.  3d  edition.  i6mo,  boards.  New  York, 
1898.  $0.50 

Halsey.  Slide  Valve  Gears ;  an  explanation  of  the  Action  and  Con- 
struction of  plain  and  cut-off  Slide  Valves.  Analysis  by  the  Bilgram 
Diagram.  79  illustrations.  7th  edition,  revised  and  enlarged. 
i2mo.  New  York,  1901.  $1.50 

• Worm  and  Spiral  Gearing.     With  Illustrations  and  Diagrams. 

(Van  Nostrand's  Science  Series,  No.  116.)  $0.50 


LIST  OF  BOOKS. 

Le  Van.  Safety  Valves  ;  Their  History,  Antecedents,  Invention,  and 
Calculation.  69  Illustrations.  I2mo.  New  York,  1892.  $2.00 

MacCord.  Treatise  on  the  Movement  of  the  Eccentric  upon  the  Slide 
Valve,  and  explaining  the  Practical  Process  of  Laying  out  the  Move- 
ments, adapting  the  Valve  for  its  various  duties  in  the  Steam  Engine, 
for  the  Use  of  Engineers,  Draughtsmen,  Machinists,  and  Students  of 
Valve  Motion  in  general.  2d  edition.  4to.  Illustrated.  New  York, 
1883.  $2.50 

Peabody.  Valve  Gears  and^  Steam  Engines.  33  Plates.  8vo.  New 
York,  1900.  $2.50 

Rose.  Slide  Valve  Practically  Explained.  Embracing  Simple  and 
Complete  Practical  Demonstrations  of  the  Operations  of  each  Element 
in  a  Slide-Valve  Movement,  and  illustrating  the  effects  of  variations  in 
their  proportions,  by  examples  carefully  selected  from  the  most  Decent 
and  successful  practice.  Illustrated.  I2mo.  Philadelphia,  1895.  $1.00 

Spangler.  Valve  Gears.  2d  edition,  revised  and  enlarged.  8vo.  New 
York,  1900.  #2.50 

Welch.  Treatise  on  a  Practical  Method  of  Designing  Slide  Valve  Gear- 
ing by  Simple  Geometrical  Construction,  based  upon  the  principles  enun- 
ciated in  Euclid's  Elements,  and  comprising  the  various  forms  of  Plain 
Slide  Valve  and  Expansion  Gearing ;  together  with  Stephenson's,  Gooch's, 
and  Allen's  Link  Motions,  as  applied  either  to  reversing  or  to  variable 
expansion  combinations.  I2mo.  London,  1875.  $l -5° 

Zeuner.  Treatise  on  Valve  Gears,  with  Special  consideration  of  the  link 
motions  of  locomotive  engines.  4th  edition.  Translated  by  Prof.  J.  F. 
Klein.  8vo.  London,  1884.  #5.00 


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